This AC provides aircraft owners, operators (i.e., certificate holders), and the flying public with information and guidance to comply with Title 14 of the Code of Federal Regulations (14 CFR) part 91, § 91.21. Section 91.21 was established because of the potential for portable electronic devices (PED) to interfere with aircraft navigation or communication systems, and prohibits the operation of PEDs not installed aboard U.S.-registered civil aircraft while operating under instrument flight rules (IFR).