A trade row with Boeing could result in the US aerospace company “turning off” Britain’s attack helicopters, military transport aircraft and a planned fleet of submarine-detecting planes, sources said last night.

The Ministry of Defence is buying 50 Apache AH-64E helicopters and nine P-8 maritime patrol aircraft from the US government. It already operates a fleet of C-17 transport aircraft and 60 Chinook helicopters. All the aircraft are built by Boeing.

Part of the multibillion-pound deal is for the US manufacturer to provide upgrades and support for the technology on the aircraft, meaning that any breakdown in relations between Britain and Boeing could affect their serviceability. “Boeing owns the data. You buy the data. You rely on the original equipment manufacturer for the key to