FAA Aircraft Dispatcher (ADX)Flight Planning and PerformanceMedium
A dispatcher is planning a Part 121 domestic flight to an airport that has only one usable runway served by a published standard instrument approach procedure. Under the '1-2-3 rule' of 14 CFR 121.619, an alternate airport is NOT required to be listed if, for at least 1 hour before through 1 hour after the ETA, appropriate weather reports or forecasts indicate the ceiling will be at least how many feet above the airport, and visibility at least how many miles?
- A2,000 feet and 3 miles
- B3,000 feet and 5 miles
- C1,500 feet and 2 miles
- D1,000 feet and 2 miles
Show answer & explanationAnswer & explanation
Correct answer: A. 2,000 feet and 3 miles
The '1-2-3 rule' allows a domestic flight to omit an alternate if, for the period 1 hour before to 1 hour after ETA, forecasts show a ceiling at least 2,000 feet above the airport elevation and visibility of at least 3 statute miles, provided the destination has only one usable runway or approach limitations.
Why the other options are wrong
- B. Overstates the requirement beyond the regulation.
- C. Incorrect values; not the standard used in 121.619.
- D. Too low; does not meet the regulatory ceiling/visibility values.
1-2-3 Rule (Alternate Not Required)
A domestic Part 121 provision allowing dispatch without an alternate when forecast weather is well above minimums for 1 hour before/after ETA.
- 1 hour before to 1 hour after ETA window
- Ceiling at least 2,000 feet above airport elevation
- Visibility at least 3 statute miles
- Applies under 14 CFR 121.619 for domestic operations
Memory trick: 1 hour, 2 thousand feet, 3 miles — count up 1-2-3