The plane lands, travelers grab their stuff, check their phones for email and voicemail and file past flight attendants for one last 'buh-bye.' But increasingly, harried passengers are leaving something behind: their iPads.

Airlines say they are warehousing hundreds of iPads and other tablet computers and e-readers left behind by travelers. Carriers try to reunite the devices with their owners but are often thwarted by the lack of ID tags, password protection and Apple Inc.'s reluctance to track down owners based on serial numbers.

Delta Air Lines says it has several dozen unclaimed iPads in Atlanta, its largest hub, and a bunch more at other hub airports around the world. Southwest Airlines says it has a 'great number' of iPads. Virgin America Airlines says it ends up donating one or two every month to a San Francisco charity after declaring them lost causes after 30 days. (The length of time a lost item is kept varies by airline.)

'A bare iPad without any identifying feature is difficult for us,' said Delta spokesman Morgan Durrant.

After landing, travelers often grab their phones. But their thin tablets and electronic readers, typically stuffed in seat-back pockets, aren't necessarily top of mind when they rush off planes. The devices can be hard to spot if covered up by discarded papers, magazines or trash. And airlines say they see more and more kids on airplanes using iPads to watch movies and play games -- and apparently leaving them behind, too.

Logically, owners would contact airlines immediately after realizing their right hand was missing. But carriers say that often doesn't happen -- people assume the device was stolen or figure it was left somewhere else like a hotel or security checkpoint. 'Sometimes owners do not file a claim, apparently thinking that once it's lost, it's gone,' said Tim Smith, a spokesman for American Airlines.

That happens not only with iPads and electronic devices, but all kinds of passenger belongings, airlines say.

And sometimes when customers contact the airline, there aren't any identifying features to single out their iPad in the room full of devices -- they don't have the serial number or a unique case, for example. Currently, iPads come in only two colors.

In many cases, when unidentifiable devices are found, airlines use flight information and seat numbers to send emails to travelers asking if they left anything onboard. Julie Del Santo and her husband Tony left an iPad onboard a Virgin America flight to San Francisco from Palm Springs, Calif., earlier this month. The couple and their two small children had suffered a six-hour weather delay and after the midnightlanding couldn't wait to get home.

'Our minds were fried,' she said.

Twenty minutes after leaving the airport, she got an email on her BlackBerry from the airline asking her to call the local baggage office.

'Immediately my husband said, 'Oh, no. My iPad,'' she said.

The direct number was answered even though it was after midnight. After describing the device, she had Virgin America ship it FedEx to her office.

'That was a class act,' she said. From past experiences with airlines, 'it's like pulling teeth to get something back.'

Emailing potential owners by seat number doesn't work if travelers don't have contact information on file at the airline, or if the aircraft itself has flown several other trips before the lost device is discovered. Planes often don't always get cleaned thoroughly after every flight.

Some carriers say half of the iPads they find go unclaimed. That is all the more surprising since the latest versions of the popular electronic tablet have a 'Find My iPad' tracking option. An owner who has registered the device and loaded that application can track the location of the device and even send a message to it so that someone who powered it up would get a message with the owner's contact information.

The tracking option, though, has its limitations. Some owners don't set it up, and even if they do, the device has to be connected to the Internet by Wi-Fi or cellular service. An iPad locked in a baggage room at an airport may be literally left in the dark.

Virgin America, which in March collected six iPads left behind from 527,000 passengers, with a few iPads still unclaimed, invested in a massive charging station to power up lost devices. Airport workers take a photo of the device with the seat number, date and flight number written on it. When a customer calls in, the airline can search through the digital pictures.

'We are seeing fewer phones left behind, but a lot more iPads and Kindles,' said Tim Thornton, director of airport operations and guest services for Virgin America.

When phones do get left behind, airlines say they have an easier time repatriating them with owners. Airlines try to keep them charged up, figuring owners will call. Many aren't password protected or have contact information that is easily found. Sometimes simply redialing the last call connects to owners.

Kindle electronic readers are easier to reunite with owners than iPads, airlines say, because they often aren't locked with password protection. That means email addresses can be retrieved. And carriers say Amazon.com Inc. has been cooperative at contacting owners based on serial numbers.

Several carriers say Apple, on the other hand, won't help when only a serial number is identified. US Airways Group Inc. said its baggage service unit actually worked out a special relationship with Apple, but other carriers say they haven't been able to do that.

An Apple spokeswoman declined to comment.

Theft of iPads and other devices has also been a problem for travelers. Airlines say they police their cleaning crews and often require two people to work a plane at the same time. While cleaners turn in many expensive computers and some wallets full of cash, there also have been instances of workers getting caught pocketing found valuables.

Worse, baggage handlers and Transportation Security Administration officers have been caught stealing valuables from checked luggage. Some have been arrested for removing items they've seen on X-ray images of luggage -- they know right where to grab.

In January, TSA officer Clayton Keith Dovel was accused of taking eight iPads from bags checked at Dallas-Fort Worth International Airport. He has been charged with theft by a public servant after one victim said he used 'Find My iPad' to track the device to Mr. Dovel's home in Bedford, Texas.

Airlines exclude valuables and computerequipment from liability and reimbursement if luggage is lost or stolen, and travelers should always carry computers, cameras and jewelry with them onboard rather than checking it in luggage.

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How to safeguard data and personal information on iPads, tablets and e-readers:

-- Apple can engrave information on the back. Securely taping a business card to the device works, too.

-- Buy a brightly colored case that is easy to spot in a messy airplane cabin. A unique case will also help airline personnel locate the device in a storage room.

-- Enable cloud storage for sensitive data, such as Apple's iCloud, Google Drive or Dropbox.

-- Go to settings on your iPad and enable Find My iPad.

-- Set up your screen saver to display a phone number that someone can see even if the device is locked.

-- Keep serial numbers of all devices in a safe place. That will help the manufacturer's customer-service representatives offer guidance.

-- When purchasing a plane ticket, provide a phone number that the airline can use to contact you.

-- Write down flight numbers and seat assignments for each leg of your trip to help airline personnel narrow their search.

-- Contact the airline immediately and file a claim. Check the carrier's policy on how long an item is kept before being donated or sold to a third-party company.

-- On iPads, enable Find my iPad. The location of the device will be displayed on a map. It can play a sound -- overriding volume or silent settings -- to help with the search.

-- On the Samsung Galaxy Tab, enable the Find My Mobile feature to trace the location of the device.

-- On the Kindle Fire, Nook, Sony and other e-readers, go online or call customer service to de-register the device. That keeps anyone who finds it from making purchases using credit-card information associated with the device. Also cancel any automatic subscriptions until the device is found.

-- On iPads, go to the iTunes store to cancel any automatic subscriptions and remove credit-card information associated with the device.