Southwest Airlines is ending its open seating policy, opting for assigned and premium seating options. It’s a substantial change for the budget airline that has let passengers pick their seats after boarding since its founding more than 50 years ago.

But tradition takes a backseat when the bottom line is suffering. Despite a record $7.4 billion in revenue for the second quarter, the airline’s quarterly profit ($367 million) was almost cut in half compared to the same period last year.

Meanwhile, activist investor Elliott Management’s $1.9 billion stake in Southwest has it calling for big changes. And the airline manufacturer Southwest relies on is going through its own crisis. So yes, something had to give.

A timeline on when the change will occur wasn’t announced — more details are coming in September — but the impact is already estimated to be big. Between paid seat assignments and premium seating, Southwest could add as much as $3 billion in new revenue, according to one analyst.

Southwest isn’t alone in its struggles. Prior to the announcement, the S&P 500 Passenger Airlines index was down almost 9%. The issue? Despite an influx of demand, there are simply too many cheap, economy-class seats on the market, writes Business Insider’s Benjamin Zhang.