The A-frame is the front section of the Airstream chassis that is visible in front of the body.
Airstream's chassis is a ladder frame steel free-standing, self-supporting chassis. Steel outriggers are utilized for additional support and strength. The A-frame is usually about three feet long and is included in the total length that is measured and listed for each Airstream travel trailer.
The propane tanks rest on it and it's also where the hitch is attached which connects to the tow vehicle.