Foreign investment in air transportation is subject to reciprocity.
"Article 25: With respect to domestic air transportation, the State Secretariat of Civil Aviation shall examine and judge capacity and quality of the Air Operator Certificate applicant and the AOC issuance must be consistent with the public interests. With respect to international air transportation: 1- In the case of the international air carrier, in addition to the criteria stipulated in the above paragraph, the State Secretariat of Civil Aviation shall consider existing international conventions of which the Kingdom of Cambodia is a signatory party with mutual understanding and reciprocity; 2- With respect to a foreign air carrier, the State Secretariat of Civil Aviation shall issue the certificate if such issuance is consistent with the international conventions or agreements of which the Kingdom of Cambodia is a signatory party with mutual understanding and reciprocity; and 3- The air transport enterprises as stipulated in the first and second paragraphs shall accept as the priority civil aviation personnel with Khmer nationalities to employ their  enterprises." (Law on Civil Aviation of the Kingdom of Cambodia, Royal Decree NS/RK/0108/003 of 19 January 2008, Art. 25)
Law on Civil Aviation of the Kingdom of Cambodia, Royal Decree NS/RK/0108/003 of 19 January 2008, Art. 25.
[<a href="http://www.vertic.org/media/National%20Legislation/Cambodia/KH_Law%20on%20Civil%20Aviation.pdf">Law</a>]