Aerogrammes (air letters) were first introduced in Cambodia in 1971. After 1979 the Phnom Penh administration issued new aerogrammes again but they did not gain popularity.
Civilians were first free to send letters after the post office operated again. Although international postage was not cheap in the following years, people least prefered aerogrammes. The postal stationery was not welcome in poverty-plagued Cambodia primarily because of the price.
Below are two aerogrammes issued in 1984, one depicted wild dogs and the other commemorate the Los Angeles Summer Olympics, each of them bear 6 riels postage:
Postage of mid 1980s can be observed from these covers:
World destinations are grouped into zones for easy postage calculation, in general the Americas have the highest rates, Europe and Africa come the second. From 1984 till mid 1985, it took no more than 5r as the highest basic rate, obviously a 6r aerogramme did not serve its expected duty properly - aerogrammes are supposed to be at a preferential postage, or at most, the same postage as regular airmail.
In 1986, inflation started to kick off. Look at this June 1986 airmail to USA:
Stamps on front and back added up to be 43.3r, nearly ten times higher than the postage a year ago. In the following years riel kept ruthlessly depreciating.
The aerogrammes were too expensive to use when issued and then later in a flash they virtually became obsolete. It had to wait till more than a decade later when Cambodia issued another aerogramme.