They'll never take delivery of these planes. They can't pay for them.

I'd be willing to bet that they are more likely financed at greater than 100%. United needs cash now badly and the manufacturers need orders. Say United orders $10B worth of jets financed at 110% (or some other similar arrangement), they just got a $1B cash infusion and Boeing/Airbus just got to put $10B worth of orders on the books.

It seems great now but it'll all come to a horrible end when United doesn't survive or can't pay up.