A question of scope
 

So, I know that United can't have over a certain number of 70 seat jets and the limit has already been reached. There is a limit for 50 seat United partner jets but that its hundreds more than are in service now.

I was also told that the flying UAX regionals do can't be more than a % of flights mainline operate.

Now here is the tricky part. Yesterday a Capt tells me that the % cap of flying UAX does only applies to 70+ seat jets, not 50 seat jets. So hypothetically ZW, XJT and Commutair could operate with all of United mainline grounded. Surely that can't be the case?

The 50 seat jets are limited as a percentage of mainline block hours, not flights. The reason that people think that they are unlimited is that the percentage allowed more 50 seaters than United wanted to operate. To answer your question, no, the regionals can’t operate with mainline grounded. Everyone is going to be affected in this deal. It looks like United is going to be smaller for a while, which will affect scope percentages. The company has also said numerous times that there will be a significant reduction in 50 seat flying after this. When it comes to what all of that means, your guess is as good as anyone’s.

It’s a percent of a rolling 12 month look back. So, yes they could ground all of UA for a period. As long as the 12 month look back is complied with.