What is the difference between estimated off-block time and estimated time of arrival?

Estimated off-block time is when the aircraft is expected to start moving from its parking position, while estimated time of arrival is when the aircraft is expected to reach a specific point, usually the destination.

How do you update ETA during flight?

ETA is revised by using actual in-flight parameters such as wind, speed, and actual departure time to recalculate the expected arrival time at each waypoint.

What time format is used for ETD and ETA in flight plans?

Both ETD (Estimated Time of Departure) and ETA are entered in 4-digit UTC format in flight plans.

When is the ETA column completed in the operational flight plan?

The ETA column is completed after the actual take-off time is known, by adding planned leg times to the departure time.

Does ETA include taxi time?

No, ETA calculations for waypoints or destination aerodrome are based on airborne time, not including taxi time.

Time of Departure and Estimated Time of Arrival

Medium4 min readFlightplanning

Moderately Examined

Why this matters

Accurate understanding and calculation of departure times and ETAs are crucial for safe, efficient operations, enabling timely coordination with ATC and effective fuel and contingency planning throughout the flight.

Understanding the time of departure and estimated time of arrival (ETA) is fundamental to accurate flight planning. The time of departure, typically recorded as the estimated off-block time (EOBT), marks when an aircraft is expected to start moving for departure. ETA is the predicted time the aircraft will arrive overhead a specific point, such as the destination aerodrome or a waypoint, based on planned or updated flight parameters.

Quick Check

In an ATC flight plan filed before departure, what does the time entered as the departure time represent?

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In depth

Explanation

Time of Departure in Flight Planning

In an ATC flight plan, the time of departure is entered as the estimated off-block time (EOBT) in UTC. This is the moment the aircraft is expected to begin taxiing, not the actual take-off time. For pre-flight filing, the EOBT is combined with the departure aerodrome's ICAO code. For in-flight re-filing, procedures differ but still require precise time notation.

Estimated Time of Arrival (ETA) Explained

ETA is the calculated time the aircraft is expected to arrive over a specific point, such as a waypoint, PET (Point of Equal Time), PSR (Point of Safe Return), or the destination aerodrome. During pre-flight planning, ETA is based on planned speeds, wind, and route. Once the actual departure time is known, ETAs for each waypoint and the destination are updated by adding planned leg times to the actual take-off time.

Updating ETA In-Flight

If actual flight conditions differ from the plan—such as changes in wind, speed, or altitude—the ETA must be revised. This ensures accurate reporting and compliance with ATC expectations. The actual time over (ATO) each waypoint is recorded, and the next leg's ETA is recalculated using current conditions.

Practical Use in the Flight Plan

The operational flight plan includes columns for leg time, cumulative elapsed time, ETA, actual time of arrival (ATA), and fuel figures. The ETA is updated in real time as the flight progresses, helping crews monitor progress, anticipate fuel needs, and coordinate with ATC.

The essentials

Key Points

Time of departure in the ATC flight plan is the estimated off-block time (EOBT), not take-off time.

ETA is the predicted time overhead a specified point, based on planned or updated flight parameters.

During flight, ETAs are recalculated using actual departure time and in-flight conditions.

Leg times and cumulative elapsed times are used to update ETAs for each waypoint.

Accurate ETAs support ATC coordination, fuel management, and operational decision-making.

Actual time of arrival (ATA) is recorded at each waypoint for performance monitoring.

Flight planning forms require both estimated and actual times for effective progress tracking.

Watch out

Exam Traps & Typical Mistakes

Confusing estimated off-block time (EOBT) with actual take-off time when entering departure time.

Assuming ETA is calculated from the time the flight plan is filed, rather than from actual departure.

Mixing up ETA with ATA (actual time of arrival) in flight plan columns.

Forgetting to update ETA after changes in wind, speed, or route during flight.

Misunderstanding that for VFR flights, ETA is to overhead the destination aerodrome, not to landing.

Test yourself

Example Exam Questions

Question 2Medium

How is the Estimated Time of Arrival (ETA) at a waypoint calculated during flight planning?

Question 3Easy

For a VFR flight, what does the total estimated time in the flight plan represent?

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