But FedEx also said it was delaying the delivery of 11 777 aircraft given adjustments to its network, particularly in Asia, in response to recent inventory destocking trends.
"But a great deal of it concerns our most sensitive systems, including aircraft avionics, surveillance technologies, satellite communications systems, and network security protocols, " he said.
The contract for the ADS-B ground station network requires continual independent validation of the accuracy and reliability of ADS-B and aircraft avionics signals.
The United spokeswoman said it hasn't substituted larger aircraft on the affected routes because those planes are being used on other parts of the route network of the Chicago-based carrier, which was formed by the 2010 merger of United Airlines and Continental Airlines.