On October 31, 2013, after outcry from media outlets, including heavy criticism  from Nick Bilton of The New York Times, the FAA announced it will allow airlines to expand the passengers use of portable electronic devices during all phases of flight, but mobile phone calls will still be prohibited. Implementation will vary among airlines. The FAA expects many carriers to show that their planes allow passengers to safely use their devices in airplane mode, gate-to-gate, by the end of 2013. Devices must be held or put in the seat-back pocket during the actual takeoff and landing. Mobile phones must be in airplane mode or with mobile service disabled, with no signal bars displayed, and cannot be used for voice communications due to Federal Communications Commission regulations that prohibit any airborne calls using mobile phones. If an air carrier provides Wi-Fi service during flight, passengers may use it. Short-range Bluetooth accessories, like wireless keyboards, can also be used.
Try to answer this question if possible (otherwise reply "unanswerable"): Where must devices be put during actual takeoff and landing?
seat-back pocket