Southwest Airlines decision to cancel about 300 flights and then ultimately grounding 79 planes (about 1/7 of its fleet) will inconvenience passengers and will cost the airline several million dollars. The damage to Southwest's earnings will be reduced if stranded passengers rebook on other Southwest flights. But other airlines such as United offered standby seating for the stranded passengers.
The grounded planes are 137-seat Boeing 737-300s. Using the airline's most recent available figures for average occupancy, it's possible to estimate that more than 31,000 paying passengers were stranded Saturday. Southwest says on its website, updated this week, that its average one-way fare is $130.27, which would produce a $4.1 million loss in revenue. Southwest might provide an estimate on the cost of grounding this month, when it releases its first-quarter earnings report.
The airfare isn’t the only loss that Southwest will have, the added expense of accessing the true damage of each aircraft and then making the FAA and NTSB mandated repairs to get their fleet back in the air must be considered. (JetBlue stated that it lost $30 million due to late-December storms that caused it to cancel 1,400 flights.)
Taking it a step further there are 931, 737-300 such models in service worldwide, 288 of which are in the U.S. fleet. Boeing said its service bulletin will also require checks on larger 737 models too. So this will stretch much farther than Southwest.