Contrail avoidance playbook (cut warming fast)

Short answer: Contrail avoidance cuts aviation warming quickly by making small route changes (often a minor climb or descent) so a plane does not fly through ice supersaturated regions (ISSRs), where persistent, warming contrails form. The big idea is targeting: less than 3% of flights can create about 80% of contrail warming, so you can get big gains by changing a small set of flights.

What this playbook helps you do

This playbook is for airline ops, dispatch, ANSP/ATM teams, and sustainability teams. It shows how to run a pilot and scale it into a repeatable contrail management program. It is designed to be ready for reporting needs such as contrail MRV (monitoring, reporting, verification).

• Cut warming fast: reduce warming from contrail cirrus, which can be as important as aviation CO2 in the near term.
• Keep safety first: changes are like storm or turbulence avoidance, done inside normal safety rules.
• Control trade-offs: manage fuel burn, added CO2, airspace capacity, and controller workload.
• Prove results: verify outcomes with satellite contrail detection and good data logging.

Key terms (plain language)

Contrails and persistent contrails

A contrail is a line-shaped cloud that can form behind a plane. Some contrails fade fast, while others last longer and spread into thin clouds. These longer-lasting ones are called persistent contrails and can trap heat, causing net warming.

ISSR (ice supersaturated region)

An ISSR is upper-air that is cold and very humid (humid enough for ice). Contrails are more likely to form and persist inside ISSRs. That is why ISSR forecasting for flight planning matters.

Navigational contrail avoidance

Navigational contrail avoidance means changing a flight path to avoid ISSRs. Most often, this is a flight level change (a small climb or descent). In some cases, it is a limited lateral deviation.

RF and ERF (warming strength)

Scientists measure contrail warming with metrics such as radiative forcing (RF) and effective radiative forcing (ERF). You do not need to be a climate expert to act. The practical rule is: avoid the worst ISSR crossings first.

Why contrail avoidance is a fast climate lever

CO2 stays in the air for a very long time, while contrails last hours. Even so, contrails can cause strong warming during that short window. That makes contrail avoidance a rare lever that can reduce aviation-attributable warming quickly using today’s aircraft and systems.

Practical implication: you do not need to change every flight. If you adjust only the highest-impact flights, you can cut warming with a small fleet-wide fuel impact.

Pre-tactical vs tactical vs hybrid: which operating concept should you use?

Pre-tactical contrail avoidance (before departure)

Pre-tactical contrail avoidance flight planning happens when dispatch can access an ISSR or contrail-risk forecast early enough. The flight plan is built with contrail risk alongside time and fuel. This reduces in-flight workload and is easier to document.

• Best for: routes with good forecast coverage and repeatable planning.
• Strength: lower in-flight workload; easier to document and verify.
• Weakness: depends on forecast skill; may need updates close to departure.

Tactical contrail avoidance (in flight)

Tactical contrail avoidance is used when the best information is available later or conditions change. The decision is made in flight, often as a small flight level change coordinated with ATC. It can increase controller workload in busy airspace.

• Best for: late or uncertain forecasts and dynamic airspace.
• Strength: flexible; can react to real conditions.
• Weakness: can add controller workload and reduce sector capacity.

Hybrid (recommended for pilots and scale-ups)

Many programs start with pre-tactical planning and keep tactical options for edge cases. A hybrid approach can be easier to scale because you can start small and learn. It also supports iterative improvements to targeting and coordination.

The contrail avoidance playbook: pilot to scale in 8 steps

Step 1: Set scope, goal, and rules

Make the program easy to run by writing down guardrails first. Keep the objective tied to persistent contrail warming, not just visible contrails. Set limits for safety, compliance, and fuel.

• Goal: reduce warming from persistent contrails.
• Scope: start with one region (for example, North Atlantic tracks) or one aircraft family.
• Safety and compliance: do not break fuel reserves, turbulence rules, or aircraft limits.
• Fuel cap: set a maximum extra fuel burn per targeted flight (for example, 0.5% to 3%).
• Targeting rule: only adjust flights above a risk threshold.

Step 2: Build the minimum data set

You need enough data to decide what to change and enough to verify outcomes later. Focus on the flight trajectory, the relevant weather fields at cruise levels, and a contrail-risk indicator. Capture operational context so you can explain why a change was or was not made.

• Flight data: route, planned and flown altitude profile, time, position.
• Weather: temperature and humidity forecasts at cruise levels.
• Contrail-risk model output: ISSR probability and persistence likelihood along the path.
• Fuel and performance: expected burn for candidate deviations.
• Operations notes: ATC constraints, turbulence, and reasons a change was not possible.

Step 3: Prioritize flights with a simple scorecard (artifact 1)

Contrail warming is concentrated, so choosing the right flights is the first job. Use a scorecard that combines climate risk and operational feasibility. Start with a narrow set of clear, high-confidence cases.

Scorecard factor	How to score (simple)	Why it matters
ISSR likelihood	Low / Medium / High	Higher means more chance of persistent contrails
Expected warming per km	Low / Medium / High	Some ISSRs warm more than others
Deviation feasibility	Easy / Possible / Hard	Can you climb or descend safely and legally?
Airspace congestion	Low / Medium / High	High congestion raises workload and delay risk
Fuel sensitivity	Low / Medium / High	Some flights pay more fuel for the same change

Target rule example: start with flights that are High ISSR likelihood + High warming + Easy/Possible feasibility. Ignore the rest in the first pilot.

Step 4: Choose the intervention type using a decision matrix (artifact 2)

Situation	Best move	Who leads	Notes
Good forecast 6 to 24 hours before flight	Pre-tactical altitude change	Airline dispatch	Often a small climb or descent avoids an ISSR
Forecast uncertain, but strong signal near departure	Hybrid: plan + allow tactical update	Dispatch + ATC	Set a clear trigger for an in-flight change
Busy sectors or capacity constraints	Avoid lateral reroutes; prefer small vertical changes	ANSP/ATM	Minimize workload and knock-on delays
Close to descent; step climbs not available	No action or very limited action	Pilot + ATC	Do not force changes late in flight
ISSR layer is thin (narrow altitude band)	Vertical avoidance	Dispatch or ATC	Often the lowest-cost option
ISSR is wide (many levels)	Consider a small lateral change, or skip	Dispatch + ATC	Only if airspace and fuel allow

Step 5: Generate and compare candidate trajectories (flight trajectory optimization)

You do not need perfect optimization to act, but you do need safe, repeatable comparisons. Create a baseline and a small set of alternatives. Compare fuel, CO2, contrail risk, and ATC complexity consistently.

1. Baseline: original plan (fuel-optimal or time-optimal).
2. Candidate A: small climb (example: +2,000 ft for 10 to 20 minutes).
3. Candidate B: small descent (example: -2,000 ft for 10 to 20 minutes).
4. Candidate C (optional): short lateral offset around the highest-risk segment.

For each candidate, record:

• Estimated change in fuel burn (percent and kg)
• Estimated CO2 change (kg)
• Estimated change in contrail risk (percent or score)
• ATC complexity risk (Low / Medium / High)

Step 6: Coordinate the operating model (airline-led, ANSP-led, or collaborative)

Contrail avoidance affects multiple stakeholders, so pick a clear operating model for your pilot. Define who proposes, who approves, and how decisions are communicated. Keep the model simple enough to operate under real workload.

• Airline-led (dispatch driven): best for pre-tactical changes filed in the plan.
• ANSP-led (ATM driven): best for tactical changes at scale in controlled airspace.
• Collaborative: dispatch proposes options; ATC clears the safest and least disruptive one.

Workload note: contrail avoidance can raise controller workload and reduce capacity in some settings. Start small, measure impacts, then expand.

Step 7: Fly, log, and label every decision

Good logging turns a pilot into a scalable program. Record outcomes consistently, including when avoidance is not attempted or is denied. Capture enough detail to support later verification.

• Log the “why”: avoided, attempted but denied, or not attempted (and reason).
• Log the “what”: exact time, position, and altitude of the change.
• Log the “context”: turbulence, weather deviations, traffic, and safety constraints.

Step 8: Verify outcomes and report (artifact 4)

Verification builds trust, improves forecasts, and prepares you for MRV. It should be repeatable, auditable, and honest about uncertainty. Store evidence and labels with each flight record.

How to verify contrail avoidance (MRV-ready checklist)

What “verify” means here

Verification answers two questions. First: did a contrail form based on observation? Second: did your change reduce warming as a best estimate with uncertainty?

1. Did a contrail form? (observation)
2. Did your change reduce warming? (best estimate, with uncertainty)

Verification methods you can use now

• Satellite checks: compare imagery and contrail-detection outputs near the flight track and time.
• Model-based attribution: use meteorology and aircraft parameters to estimate persistence and warming potential (RF/ERF proxy).
• Counterfactual design: compare an avoided flight to a similar non-avoided flight, or the same flight on a nearby day with similar conditions.
• Onboard data (emerging): humidity sensors can help confirm when an aircraft is inside an ISSR, but this is not yet universal.

MRV-ready checklist (copy/paste)

Contrail Avoidance MRV Checklist
1) Flight ID and date/time
2) Planned route and planned flight levels
3) Flown trajectory (time, lat, lon, altitude)
4) Forecast used (model name, run time, resolution)
5) Contrail/ISSR risk score along baseline and avoided path
6) Avoidance action taken (climb/descend/lateral) and timing
7) Fuel impact estimate (kg and %)
8) CO2 impact estimate (kg)
9) Observation source (satellite product, time window)
10) Outcome label: contrail observed (yes/no/unclear)
11) Uncertainty notes (cloud cover, forecast mismatch)
12) Summary for reporting: avoided warming estimate (range)

Tip: include an “unclear” bucket because some satellite scenes are blocked by clouds. You can still learn from those cases.

Trade-offs: fuel burn, CO2, and why targeting matters

The key trade-off is that small route changes can add a little fuel burn and CO2, but can cut a lot of near-term warming from persistent contrails. The better your targeting, the smaller the fleet-average fuel increase. Use caps and score thresholds to keep trade-offs controlled.

Use a simple fleet-average calculator (artifact 3)

This template turns “percent fuel increase on a few flights” into a fleet-wide view. It can also support a rough estimate of cost per tonne of CO2e avoided when you have an avoidance estimate per adjusted flight.

Simple Contrail Avoidance Cost Calculator
Inputs
A = flights per year
B = share of flights adjusted (0 to 1)
C = extra fuel burn on adjusted flights (0 to 1)
D = average fuel burn per flight (kg)
E = fuel price ($ per kg)
F = estimated CO2e avoided per adjusted flight (tonnes CO2e)

Calculations
1) Extra fuel per adjusted flight (kg) = C * D
2) Extra cost per adjusted flight ($) = (C * D) * E
3) Total extra cost per year ($) = A * B * (C * D) * E
4) Total CO2e avoided per year (tonnes) = A * B * F
5) Cost per tonne CO2e ($/t) = (Total extra cost per year) / (Total CO2e avoided per year)

Sanity checks
- Report fleet-average fuel change = B * C
- Keep B small by targeting high-impact flights

Anchoring data point: one large field study reported pilots using AI-based predictions reduced contrails by about 54% on test flights, with about 2% more fuel on those adjusted flights. If only a small share of flights needs changes, this can translate to roughly 0.3% more fuel fleet-wide.

Sensitivity table (quick planning view)

What changes	What to watch	Program response
Higher forecast uncertainty in humidity	More false alarms or misses	Use bigger safety margins; verify and retrain; start with highest-confidence cases
Congested airspace	Controller workload and delays	Prefer pre-tactical; limit tactical requests; coordinate sector plans
More fuel burn than expected	CO2 increase and cost	Tighten fuel caps; favor vertical moves; improve trajectory comparisons
Low verification coverage (cloudy satellite scenes)	Harder proof	Use multiple observation sources and longer time windows; keep an “unclear” bin

Common constraints (and how to handle them)

1) You cannot avoid what you cannot forecast

ISSR prediction skill is improving, but it is not perfect. Treat forecasts like turbulence forecasts: useful but not exact. Start where forecast skill is best, then use verification to improve.

• Do: start where forecast skill is best; use verification to improve.
• Do not: reroute many flights based on low-confidence signals.

2) System effects are real

If many aircraft request similar changes, network effects can appear: lower capacity, more delays, and extra fuel across the system. That is why targeting and coordination with air traffic management (ATM) are central. Scale should follow measured impacts, not assumptions.

3) Safety comes first, always

Contrail avoidance should never compete with core operational and regulatory requirements. If there is a conflict, do not make the contrail-related change. Treat it as optional and reversible.

• turbulence and storm avoidance
• minimum fuel reserves
• aircraft performance limits
• ATC separation rules

Program blueprint: what to do in the first 2 to 4 weeks

Week 1: Design

• Pick one region and one fleet group
• Agree on fuel caps and targeting rules
• Choose a forecast source and verification method

Week 2: Build

• Implement the scorecard in dispatch planning
• Create a standard message for ATC coordination
• Set up the MRV checklist and logging fields

Weeks 3 to 4: Pilot and review

• Run a small number of flights (start with dozens, not thousands)
• Measure contrail outcomes, extra fuel, delays, and workload notes
• Publish a short internal report with results and changes for the next cycle

FAQ (search-aligned)

What is an ice supersaturated region (ISSR) and why does it matter?

An ISSR is cold air with enough humidity for ice. Persistent contrails are much more likely in ISSRs. Avoiding ISSRs is therefore the core of contrail avoidance.

How to avoid persistent contrails with small altitude changes?

Use an ISSR forecast, then plan a short climb or descent around the highest-risk segment. Many cases require only a small flight level change for a limited time. Apply fuel caps and avoid changes that increase operational risk.

How many flights cause most contrail warming?

Contrail warming is highly concentrated. A widely cited estimate is that less than 3% of flights generated about 80% of contrail warming in a recent year. That is why a targeting scorecard can outperform broad, low-precision actions.

Does contrail avoidance increase CO2 emissions?

It can, because extra fuel burn means extra CO2. When you target only the highest-impact flights, the fleet-average fuel increase can be small. That can still deliver large near-term warming reductions from contrails.

How do you verify contrail avoidance using satellite imagery?

Match the flown track and time window to satellite images and a contrail-detection product. Label outcomes as yes, no, or unclear. Store the label and the evidence with the flight record for auditability.

What is contrail MRV and why does 2025 matter?

MRV means monitoring, reporting, and verification. Some jurisdictions are moving toward formal reporting of contrail climate impact starting around 2025. Strong logging and verification workflows reduce risk and rework later.

Takeaways

• Contrail avoidance is one of the fastest ways to cut aviation warming using today’s operations.
• The smartest approach is targeted contrail management: change a small share of flights that drive most warming.
• Choose pre-tactical, tactical, or hybrid based on forecast timing and airspace constraints.
• Build trust with a simple, repeatable verification method and MRV-ready logs.
• The biggest climate risk is delay: starting small now creates the learning loop that makes scale possible.