Ever been on a plane and wondered whether your luggage made the flight?

Now, American Airlines passengers can track their checked bags - in real time - by going to the American website, and typing in bag claim information.

American, which transports 76 percent of air travelers in Philadelphia, introduced the service on Aug. 21.

Carriers that offer real-time luggage tracking include US Airways, which is now part of American, and Delta Air Lines. Southwest and United Airlines do not offer the service.

Delta was the first U.S. carrier to launch real-time baggage tracking. "We debuted this in April 2011 on delta.com and later on the Fly Delta app," Delta spokesman Morgan Durrant said.

"It's one of the most popular features of the app after check-in. It's safe to say that it gets millions of uses a year," Durrant said.

United is developing an online baggage-tracking service, airline spokesman Charles Hobart said.

Here's how the American bag-tracking works:

Go to AA.com/baggage, click on "track your bags," and type in the traveler's last name and flight confirmation code, or bag-tag number, and the status of the bag pops up. The baggage tracking is not available on American's smartphone app.

Checked bags are scanned four times: at passenger check-in, when loaded on the plane, when unloaded from the plane, and at baggage claim.

"This is something our customers have been asking for for a while, so we're excited to bring it to them," American spokeswoman Laura Nedbal said.

"We've always had this real-time scan data. We just didn't have a means to make it transparent to our customers," Nedbal said.

The technology tells fliers the bag's status, such as "loaded on the plane," the airport location, date, local time, and flight number.

If the bag does not make it to the passenger's destination, "you can go straight to baggage-services desk and fill out a claim," Nedbal said.

If you are on the plane and suspect your bag did not make it, you must deal with it at your destination.

Passengers transferring from another airline, such as British Airways or Lufthansa, can track their bags only after they have been handed over and scanned by American.

American sees the service as another tool to reduce the rate of mishandled bags. In July, American had 3.73 mishandled bag reports filed per 1,000 passengers, compared with 3.91 reports in July 2014, according to the Department of Transportation Air Travel Consumer Report.

"This is one more way for our customers to have a more seamless experience, and for them to see exactly where their bag is so that they can rest easy," Nedbal said.