New York LaGuardia, New York JFK and Washington National airports are ‘slot controlled’. That means there are limits on the number of takeoffs and landings at each airport, and the right to use those have been given (free!) to incumbent airlines as a property right. That’s a huge subsidy to incumbent carriers.
Normally slots come with ‘use it or lose it’ rules. If an airline doesn’t make use of their slots 80% of the time, those slots can be reassigned to another carrier. As a result you’ll see airlines flying more or less ghost flights, service designed to hold the slot rather than meet any economic need.