Both chopper and copter have been widely used as abbreviations of helicopter since that craft became a military mainstay in the 1940s and ’50s. Copter was more common than chopper until the 1990s. Chopper is now more common, but copter may be making a comeback. This is a positive trend, as chopper has numerous other meanings, including (1) a tool used for chopping and (2) a customized motorcycle, and hence can cause confusion. Copter has no other definitions, so it is safer.
Examples
Many major publications use copter—for example:
Missile Is Fired at Copter Over Baghdad, U.S. Says [NY Times]
… the company issued a notice in January urging replacement of the studs, telling operators of the copter to substitute the parts within a year or 1,250 flight hours. [Globe and Mail]
Laser blinds copter pilot carrying sick patient [Sydney Morning Herald]
But chopper still prevails, and it may continue to prevail despite the potential confusion. For example, it appears in these major publications:
A list released by his office of all the chopper trips does not include any flights to the governor’s shore house … [Washington Post]
Soldiers kept firing their machine guns into the air, to be followed later by a chopper circulating around our heads. [Guardian]
Police were waiting when they returned to the chopper and it was flown to the airport under onboard escort. [New Zealand Herald]
