Just to cover the 'does X airline allow it?', here's a quick gathering of airline rules regarding personal electronic devices, from their current websites. Note that not a single one allows scanners (AM-FM transmitters-receivers) in flight.
American Airlines:
Electronic Equipment/Personal Devices
All portable electronic devices must remain off and properly stowed during taxi, takeoff, approach, and landing
until the plane is at the gate and the seat belt sign is off. Cellphones may be used on certain aircraft after
landing in the U.S., the U.S. Virgin Islands, and Puerto Rico, once authorized by a flight attendant. Your flight
attendant will tell you when you may use approved portable electronic devices in-flight. Devices with transmitting
capabilities may only be used if the transmit capability is turned off and can be verified by a flight attendant
(example: combination cellphone/PDA devices or laptop computers with wireless capabilities). During flight, never
use cellphones (to make or receive calls), two-way pagers, radios, TV sets, remote controls (example: DVD, CD,
game, or toy remote controls), a cordless computer mouse, commercial TV cameras, or Global Positioning Systems.
Radio transmission using personal communications devices (example: walkie-talkies, two-way pagers, or wireless
headphones) is prohibited, as it may interfere with the aircraft's communications and navigation systems.
Devices that could cause damage to equipment or that may diminish the design, function, or capability of the
aircraft are prohibited. You may use audio and video devices only with a headset. Use of still and video cameras,
film or digital, is permitted only for recording personal events. Photography or video recording of airline
personnel, equipment, or procedures is strictly prohibited.*
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Continental Airlines:
Electronic DevicesLiability
Continental will not accept liability for computers or computer related equipment when accepted as checked baggage. Small laptop computers may be considered as carry-on baggage.
Personal Electronic Devices
It has been determined that certain electronic devices could cause minor interference with aircraft navigational instruments. Therefore, restrictions on the use of personal electronic devices are necessary.
Passengers may turn on and use cellular phones only when the main cabin door is open. Pagers may be used to receive messages at any time.
Devices that may be used only when announced by the flight attendants and the aircraft is above 10,000 feet in altitude:
electronic games
personal computers
entertainment players
recorders (audio and/or video, such as tape/CD/MiniDisc/MP3 players and camcorders)
calculators
shavers
cameras
aircraft power ports for laptops.
Devices that are not permitted for use at any time:
battery operated personal air-purifying device
TVs
radio receivers and/or transmitters (including AM/FM/SW, CB and scanners)
remote-control toys.
Passengers must not wear Continental-provided headsets and should not wear personal headsets during taxi, takeoff and landing.
Passengers may always use any medically prescribed, physiological instrument, such as a hearing aid or a pacemaker.
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Delta Airlines:
Portable Electronic Devices
It's never been so cool to be a geek but there's a few things you'll need to know about operating your gadgets
on board our planes. Your flight crew will remind you again, but it's always good to know ahead of time.
While these are good general guidelines, remember that the flight crew may, at any time, ask you to turn off
a portable electronic device for safety reasons.
Devices You Can't Use
For safety reasons, you may not operate the following devices onboard:
Two-way transmitters such as walkie-talkies, amateur radios, citizen band (CB) radios, 49 MHz transmitters
Devices designed to radiate radio frequency energy on specific frequencies
Peripheral devices for computers or games connected by cable
AM/FM radios
Portable television sets
Remote control toys
Devices You Can Sometimes Use
You can only use these devices while the plane is at the gate with the doors open or after the plane has landed
and is taxiing to the gate.
cellular phones
one and two-way pagers
You can use the following devices while the plane is at the gate with the doors open, after the plane has taken
off and reached its cruising altitude and before it begins to descend for landing.
Personal computers
Personal computer peripheral devices
Compact disc players
Digital cassette tape player/recorders
Video recorder/playback systems
Calculators
You can use these while the plane is at the gate with the doors open, after the plane has taken off and reached
its cruising altitude and before it begins to descend for landing, and after the plane has landed and is taxiing
to the gate.
Personal digital assistants
Personal computer games
GPS (global positioning satellite) systems
Your flight attendant will announce when it is safe to use these devices.
Devices You Can Always Use
You may use the following devices at any time:
Hearing aids
Heart pacemakers and other implanted medical devices
Electronic watches
Electronic nerve stimulators
Electric shavers
Delta's installed equipment
Acceptable personal life support systems and accompanying pagers
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United Airlines:
Electronic devices
Certain electronic devices may not be used on our planes for safety reasons. Such devices may cause electromagnetic
interference with cockpit navigation or communications systems during ground operations and while the aircraft is
flying below 10,000 feet. However, when an aircraft is traveling above 10,000 feet (normally about ten minutes
after takeoff), passengers can use many of the devices listed.
Hearing aids, heart pacemakers, and watches are acceptable at all times.
These electronic devices can be used in the cabin, but may not be used during takeoff and landing:
Calculators
Handheld computer games
Shavers
Portable CD and tape players
Laptop computers/accessory printers/tape drives
Portable VCRs/video players
These electronic devices cannot be used on the airplane at any time:
Cellular phones (cellular phones maybe used on the plane at the gate before the aircraft door is closed or at
captain's discretion when the plane is away from the gate and on the ground)
Televisions
AM/FM transmitters-receivers
Remote-controlled toys
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Northwest Airlines:
Electronic Devices
On board the Aircraft: Certain electronic devices may not be used on Northwest aircraft for safety reasons.
Such devices may cause electromagnetic interference with cockpit navigation or communications systems during
ground operations and while the aircraft is flying below 10,000 feet. However, when an aircraft is traveling
above 10,000 feet (normally about ten minutes after takeoff), passengers can use many electronic devices.
Electronic devices that can be used at all times
Hearing aids
Heart pacemakers
Watches
Electronic devices that can be used on board the aircraft, but may not be used during takeoff and landing:
Laptop computers
Portable CD and tape players
Calculators
Portable DVD players
Handheld computer games
Electronic devices that cannot be used on the airplane at any time:
Cellular phones
AM/FM transmitters-receivers
Televisions
Remote-controlled toys
Personal Air Purifier
Personal Camera Equipment: Northwest allows passengers to carry on cameras in addition to the normal carry-on
luggage allowance.