That's definitely a huge contributor to the success of the A350.

The 777 is thoroughly established at this point, and on the surface looks like the safer bet for new widebodies given the availability of parts and labour.

But when you actually look at orders and forecasted production, the wait times are about the same for either plane at this point. And with 600 open orders, even if they never get a single new purchase after today, it's not like the A350 is going to be a hard plane to find parts for.

At this point, it's all down to price and priority. If Airbus is willing to commit to a faster delivery than Boeing for a comparable or better price, United would be foolish to turn them down. Sure, there are costs around standing up new maintenance and flight ops programs that Airbus will have to offset with deeper discounts, but they still come out ahead in the long run with an entrenched customer and a foot in the door at an airline that historically prefers Boeing widebodies.