Final answer:
Trans-polar aircraft operations require multiple communication systems to avoid interference with ATC by using high frequencies like microwaves, which need a clear line of sight.
Step-by-step explanation:
Trans-polar operators need to be equipped with various modes of communication to maintain contact with ATC during the entire flight. Important communications on airplanes and in hospitals require the use of radio frequencies similar to those used by mobile phones, typically around 1.9 GHz. Interference with these systems could affect their operation, leading to the requirement of switching off or putting mobile devices into a noncommunicative mode. Additionally, high frequencies such as microwaves are suitable for carrying more information and are predominantly used in satellite and long-distance communications, necessitating a clear line of sight due to short wavelengths.