Yes, it can, and the 3GS has a warning and shuts down when it gets to a certain temperature (I think it's like 118). I'm not sure if the 3G gives the same warning.
Operating temperature: 32° to 95° F
(0° to 35° C)
Nonoperating temperature: -4° to 113° F
(-20° to 45° C)
Relative humidity: 5% to 95% noncondensing
Maximum operating altitude: 10,000 feet (3000 m)
Operating temperature: 32° to 95° F
(0° to 35° C)
Nonoperating temperature: -4° to 113° F
(-20° to 45° C)
Relative humidity: 5% to 95% noncondensing
Maximum operating altitude: 10,000 feet (3000 m)
It has something to do with Air Pressure. A plane cabin is pressurized unless you were on that Southwest flight yesterday, so there are no problems in a plane. However I took mine when I climbed a 14er here in CO and had no problems (14,060 feet).