Abbreviation of 航空郵便. Refers to the postal service that sends letters and parcels by air.
See also: 航空郵便
Please send this letter by airmail.
air service; air transport (of goods)
General term for transportation of cargo by air, not limited to postal mail.
Perishable foods are transported by air service.
I sent that letter by airmail.
The item I ordered arrived by air shipment.
The package is urgent, so please send it by air.