Permits Aircraft to Take Off With Minor Wing Frost at Pilot Discretion

The FAA has granted Allegiant Air an exemption to take off with its Boeing 737 MAX 8-200 aircraft even if there is icing on a specific part of the wing. The filing was submitted on November 5 and made public a day later.

Allegiant Air’s exemption request explained that frost tends to form on this area of the wing even in non-icing conditions. This could be due to the temperature of the fuel in the wings cooling down the surface.

The FAA’s decision took input from Boeing’s aerodynamic analysis and existing manuals. It determined that Boeing’s aircraft flight manual (AFM) allowed cold-soaked fuel frost (CSFF) to be present on a given zone of the wing without hindering safety.

The agency’s exemption only applies to Allegiant’s 737 MAX 8-200, so it must follow Boeing CSFF limitations with the rest of its fleet. The carrier currently operates one of this specific aircraft and is slated to receive 11 more Boeing airliners in 2025. 

There are a few exceptions to the grant. Even if the given conditions match up with the FAA exemption, the final go/no-go decision is left up to the captain. Additionally, the FAA prohibits the aircraft to takeoff with CSFF on the wing tank upper surfaces when the outside air temperature is less than 4 degrees C, the fuel temperature is below -16 degrees C, CSFF is present beyond the “safe zone,” or there is visible moisture.

Allegiant Air is still required to follow all other limitations and regulations for deicing and anti-icing operations. Before Allegiant pilots and ground personnel can take advantage of the CSFF exemption, they must undergo training to ensure they know how and when to apply it.

The approval will expire on November 30, 2026 unless it is renewed. The FAA also has the authority to suspend the exception at any time if Allegiant Air does not follow its limitations.

FMI: www.allegiantair.com