معنی First Line در این جمله

secret information revealed German plans for a first-line strength of 1,296 planes, with full reserves, by the autumn of 1936.

یا در این جمله

the German Air Force would be no larger than 500 firstline aircraft by the end of 1935

هواپیمای خط مقدم درسته؟ یا آماده به کار؟