Why are airlines canceling so many flights?

Airlines cancelled nearly 1,200 U.S. flights on Sunday and Monday, leaving passengers stranded and luggage piled up at airports across the the country, while thousands more trips were scrapped across the globe as the summer travel season kicks off. 

Now for the bad news: Airline analysts says expect delays and cancellations are likely to persist, and could even get worse.

"We may not have seen the worst of this," Kit Darby, founder of Kit Darby Aviation Consulting, told CBS MoneyWatch.