During the post-2001 crash in airline passenger demand US airlines lost more money in that one slump than all profits from all US airlines, combined, from the Wright Brothers to September 11th 2001.
That was why you had such rapid consolidation, as America West became US Airways became American, United bought Continental, and Delta bought Northwest, to remove so much competition that they could be profitable again.
https://transtats.bts.gov/Data_Elements_Financial.aspx shows 2001-2005 net income losses were 57 billion dollars, then a brief profitability in 2006-7 but the losses of 2008 and 2009 wiped that all out again (in net income terms).
I read that thing about the integral of all profits back to the Wright Brothers back around in 2010, and I can't find a good source on aviation profitability in the 1970's right now.
That was why you had such rapid consolidation, as America West became US Airways became American, United bought Continental, and Delta bought Northwest, to remove so much competition that they could be profitable again.