Another good read by Cranky Flyer on subject of one airline buying a stake in another airline.
https://crankyflier.com/2020/06/02/delta-and-the-perils-of-investing-in-partners-it-cant-control/
https://crankyflier.com/2020/06/02/delta-and-the-perils-of-investing-in-partners-it-cant-control/