Seems to be what they used to do prior to deregulation and to a lesser extent in the 90s/2000s. Every flight being full is a more recent phenomena and they are

Seems to be what they used to do prior to deregulation and to a lesser extent in the 90s/2000s. Every flight being full is a more recent phenomena and they are getting better at it over time [1]. When flights aren't full you can pull a plane out of its normal route and fly those passengers on the later one. [1] https://www.usatoday.com/story/travel/flights/todayinthesky/2018/02/01/airlines-set-record-filling-seats-planes-2017/1087532001/ https://www.usatoday.com/story/travel/flights/todayinthesky/...