By Kelli B. Grant

For all the miseries of flying with small children, families could always count on one perk from the airlines: early boarding. But now, this too seems to be going the way of the free in-flight meal.

Families hoping to avoid the crush of passengers and bags during boarding may now need to pay $36 or more for the privilege. United, is the most recent airline to stop letting families with young children board first,  reports USA Today. American Airlines dropped family pre-boarding a few years ago, and US Airways did so last year. Delta, JetBlue and Virgin America are among the few carriers that still show preferential treatment to parents.

The move is almost certainly to generate revenue, says George Hobica, founder of fare-tracking site AirfareWatchdog.com. Despite charging fees for a slew of amenities, “airlines are still losing money,” he says. Most airlines that offer a paid priority boarding option charge $9-per-person or more for the privilege, depending on the flight length. That’s potentially lucrative, especially on routes that attract a lot of families, he says. A family of four would need to pay $36 at least. Aside from avoiding the mad dash onto the plane, the main reason to board early is snagging coveted overhead bin space, Hobica says. “[Fitting your suitcase] is like musical chairs, if you’re the last person on,” he says.