ICAO Annex 2
Attachment B. Unlawful Interference
2. Procedures

2.2 When an aircraft subjected to an act of unlawful interference must depart from its assigned track or its assigned cruising level without being able to make radiotelephony contact with ATS, the pilot-in-command should, whenever possible:

a) attempt to broadcast warnings on the VHF channel in use or the VHF emergency frequency, and other appropriate channels, unless considerations aboard the aircraft dictate otherwise. Other equipment such as on-board transponders and data links should also be used when it is advantageous to do so and circumstances permit; and
b) proceed in accordance with applicable special procedures for in-flight contingencies, where such procedures have been established and promulgated in the Regional Supplementary Procedures (Doc 7030); or
c) if no applicable regional procedures have been established, proceed at a level which differs from the cruising levels normally used for IFR flight by:

1) 150 m (500 ft) in an area where a vertical separation minimum of 300 m (1000 ft) is applied; or
2) 300 m (1000 ft) in an area where a vertical separation minimum of 600 m (2000 ft) is applied.