I made a dumb mistake after my United Airlines flight was delayed--a mistake that I now realize might have cost my wife and me roughly $1,400.

And while I feel silly, my loss is your gain: I'm sharing my story so you won't make the same error. 

In short, if you're traveling to or from Europe, and your flight is delayed more than three hours, you're potentially entitled to roughly $700 in compensation under European law.

Here's my story, the European law, and how to make sure that you don't make the same silly mistake I did.

When in Rome (for 7 extra hours)...

Our story begins just over three years ago, at the end of a 10-day vacation to Italy. It was a fantastic trip, with only one hitch: my wife and I were stuck in the airport for most of our last day in Rome, because our United Airlines flight home was delayed.

We were supposed to take off at 9:55 a.m. for Newark, but the flight didn't leave until 4:48 p.m. due to a mechanical issue--almost a seven hour delay. (Shout out to FlightAware, which confirmed the exact times for me).

That was in 2015. Last Saturday afternoon, my wife and I were reminiscing about the trip.

"You know what?" I said. "I think it was three years ago today that we were stuck in Rome."

"No," my wife corrected me. She'd posted on Instagram that day, and she'd just received of those "on this day" notifications on her phone. "It was three years ago yesterday."

Okay. Fast forward maybe two hours later. I was on our couch, writing an article for Inc.com, flipping through Facebook--and I saw an ad for a company called AirHelp.

I almost choked as I read it, given my conversation with my wife:

Flight delay to/in Europe within the last 3 years? 

"According to EU regulations, when airlines cancel European flights, or delay them by more than 3 hours, they owe you $700 cash."

Yes, I realized, we  been on a flight from Europe that was delayed more than three hours! 

But, also ... it had now been three years and 1 day. Would the extra day matter?

TLDR: Yes, it mattered

I clicked the ad and filled out the intake form. Sure enough, my claim was flagged for having fallen just outside the three year window.

This was no small error. Given that both my wife and I would have been eligible, we would have potentially been owed $1,400 or more. But, I'd had no idea at all about this whole situation until I saw the ad.

Even more painful, it turns out my colleague Chris Matyszczyk wrote about AirHelp and the EU law back in March. As he pointed out, I now see, a vast majority of Americans never file claims because they don't know about the European law.

Clearly, I should read my fellow Inc.com writers' work more closely.

I asked United for comment. They didn't reply. I also reached out to AirHelp, which basically said that since I'd learned about all this a day too late, they couldn't help me.

"You may have been able to successfully file a claim for compensation from the airline," if I'd been on time, the company's CEO, Henrik Zillmer, told me in an email.

And, he also confirmed the gist of what I now understood: Due to an EU regulation called EC 261, "airlines must provide passengers affected by lengthy delays of more than three hours with compensation of up to $700 each, in addition to meals and drinks for all delays of more than two hours."

The fine print

Of course there's some really intense fine print to the European law.

First, it's potentially a lot of money that airlines have to pay out, so they're not eager. And second, this is the European Union. Nothing is ever straightforward and simple.

That said, AirHelp says it's helped more than 5 million passengers worldwide claim more than $369 million in compensation from airlines. They have a pretty comprehensive "Know Your Rights" section on their website.

They also have a tool that will go through your email accounts, check your flight receipts, and determine if you were on a European flight that could qualify you for compensation.

I'm not doing it myself. Since my Italy trip was my last trip to Europe, I know for sure there isn't some other delayed trip out there I'd forgotten about, that falls within the three year window.

But think hard. If you've been on a delayed European flight--or if you don't recall offhand whether you've been on a delayed flight, but you're comfortable giving AirHelp access to your email and receipts--it might be worth looking. I certainly wish I had.