Every Airstream I've owned (four) or seen has a 4" square plate of thin aluminum with an "X" in the center attached to the frame just behind the rear axle on each side. The owner's manual tells you this is the recommended jacking or lift point. It is apparently also the balance point, front to rear, when the hitch jack is supporting the tongue. It is also the jacking point prescribed in an old Airstream factory service manual I obtained when a local Airstream dealer went out of business.
I have always placed a chunk of 2" by 4" block in the saddle of my floor jack and gently raised it against the frame, being very careful to align the wood block lengthwise, under the frame rail, not against the belly skin on either side of the frame. After lifting the trailer off the ground at the lift point, I always slip a stack of two concrete blocks padded by a wood block as close to the jack as possible and then transfer the weight to the concrete blocks. I also then support it fore and aft with either jack stands padded by wood blocks or concrete blocks, also padded with wood blocks.
I had to replace the water tank on the 34' triple axle I previously owned so I lifted it on both sides, as previously explained, then placed concrete blocks at four points on each side, at the rear, at the front, and in front of and behind the axles. It had to remain suspended for several days so I wanted to ensure I didn't bend the frame or warp any side sheet panels. It was still scary crawling around under the monster but it held securely and didn't warp the frame or panels.
Harvey