The airport lounge ain’t what it used to be.

Once seen as quiet retreats for businessmen on expense accounts looking to get some work done, lounges are now trying to serve a variety of purposes and, in the process, have become one more area of competition among the airlines and independent operators. Some lounges are offering spa treatments and expansive views of the tarmac, and most are upgrading their food options. A few have even added playrooms for families traveling with children.

With the robust economy, more passengers than ever are willing to pay to get into the lounges, said Gary Leff, creator of the travel advice website View From the Wing. And that has added to a problem: The clubs have become victims of their own success — at times too full to accommodate all who are allowed to enter.

International business- and first-class ticket holders have always been welcomed. But now, fliers can pay for a yearlong or sometimes a day pass. In addition, credit card companies like Citi, Chase and American Express have been offering lounge access as part of their airline partnership or premium credit card offerings. And, of course, with the economy still strong, more people are traveling.

The growth and improvement in airport lounges, Mr. Leff said, “is driven by consolidation in the airline industry and competition by both airlines and credit-card issuers for the business of premium customers.”