The Federal Aviation Administration (FAA) is asking airlines to either retrofit their existing aircraft fleet with ice-detection equipment or ensure that the ice protection system activates at the proper time.

The rule requires the system to alert the crew each time they should activate the ice-detection system, with the system either turning on automatically or being manually activated.

In absence of such a system, the crew would activate the protection system with cues on their airplane’s flight manual during climb and descent and at the first sign of icing when at cruising altitude.

FAA administrator Randy Babbitt said that the administration wanted to make sure all classes of aircraft in scheduled service remained safe when they encountered icing.

The proposed rule will only apply to in-service aircraft with a take-off weight of less than 60,000lb since most larger airplanes already have the required equipment.

According to the FAA, studies show that smaller planes are more susceptible to the problems caused by undetected icing or late activation of the ice-protection system.

The FAA estimates the rule will cost operators about $5.5m to implement and affect almost 1,900 aircraft.

All turbojet airliners and many turboprops covered under the rule, however, already have equipment that satisfies the requirements.

Operators would be given two years after the final rule is effective to make these changes.