India, May 26 -- After more than 50 years of allowing passengers to check two bags for free, Southwest Airlines is making a major change. Starting Wednesday, the airline will begin charging many travelers for checked luggage, ending a long-standing policy that set it apart from most competitors. Baggage fees generated nearly $7.3 billion for U.S. airlines last year, according to federal data. With mounting pressure to boost revenue, Southwest executives, despite years of pledging to keep the "two bags fly free" policy, are now following the industry trend.

Over the past year, Southwest has introduced major shifts to its business model, including plans to eliminate open seating. Starting Wednesday, the airline will also roll out basic eco...