It was one of the worst ways airlines could treat customers: nickel and diming vulnerable parents who just wanted to sit with their kids on long flights.

Sorry, the carriers were starting to say (only they weren't sorry at all). If you want to sit near your children, you'll have to pay extra. Otherwise--again, so sorry!--your baby boy or girl might be stuck in a middle seat 10 rows away. (Probably between two not-so-happy fellow travelers, I might add.)

My colleague Chris Matyszczyk wrote about the whole thing recently. Things looked bleak. It wasn't as if there was any chance Congress was going to do anything about it, right?

Only, sit back and fasten your seat belt. Congress took everybody completely by surprise.

No more "sitting with your kid" fee

Here's what happened. The Federal Aviation Administration can only operate if Congress renews its authorization, and the law was going to expire. Which it did--only with some extra benefits. In short, it's now illegal for an airline to charge extra for a parent to be guaranteed a seat next to his or her child (under 13).

My friends at Scary Mommy did a great job summing it all up.

There are exceptions obviously. "But I have to sit with my daughter," isn't a way to get you both first-class tickets when you only paid for one.

But it's great to have a clear policy that will allow parents to supervise their own kids and keep families together on flights without having to worry about being split up or being hit with extra fees in order to sit together.

There are other benefits in the new law, too. For example, if an airline loses your luggage for 12 hours, they'll have to refund you the bag fee--even if they later find it. And, there are some measures to try to ease the lines at security.

A total surprise?

Here's the best part. Nobody really is sure why Congress suddenly acted.

Lobbyists on both sides--the consumer advocates who wanted some kind of action and the airline lobbyists who wanted to protect their fees, were both totally taken by surprise, according to The Washington Post, which first reported on the new law last week.

"This is an amazing win for consumers," Charles Leocha of Travelers United told the Post.

Airline lobbyists? Not so psyched, but equally surprised.

"We believe that provisions designed to re-regulate airline pricing and services are bad for airline customers, employees, the communities we serve and our overall U.S. economy," the Post quoted Jean Medina from Airlines for America, as saying.

Here's who to thank (maybe).

I used to be a lawyer and a reporter in Washington. I spent a lot of time on Capitol Hill, and I have a theory. It goes like this.

Somewhere, deep in the bowels of the House or Senate office buildings, there's a congressional staffer, or maybe even a representative. A mom or a dad, probably, with a couple of young kids. Probably more than one, come to think of it, who plays a role in this story.

Imagine that last year, these staffers and lawmakers were all flying their families to visit grandma and grandpa back home--Arizona or Texas or New Hampshire, wherever.

Maybe, just maybe, they all got rude awakenings when they tried to sit together with their kids on a plane.

It wouldn't surprise me at all to learn that a few of these committee staffers, or legislative aides, or even lawmakers, might have happened to be on the House or Senate Transportation committees, which oversee the FAA.

And maybe, just maybe, when it came time to renew the FAA authorization, they saw their chance to act--without regard to what lobbyists on either side of the issue had to say. I mean, just because they work in Congress doesn't mean they're not human beings.

Sure, of course there's another alternative. Maybe Congress just suddenly decided to do the right thing.

You tell me which you think is more likely.