If you are flying at FL300 in an air mass that is 15 degrees warmer than ISA, what is the OAT likely to be?

To determine the outside air temperature (OAT) at FL300 when flying in an air mass that is 15 degrees warmer than the International Standard Atmosphere (ISA), it's essential to understand the standard temperature at that altitude.

At FL300 (30,000 feet), the standard temperature according to ISA is typically around -30 degrees Celsius. Since the air mass is 15 degrees warmer than the ISA, you would add 15 degrees to the standard temperature.

Calculating this gives you:

-30 degrees (ISA at FL300) + 15 degrees (warmer air mass) = -15 degrees Celsius.

Thus, the OAT is likely to be -15 degrees Celsius, which corresponds to the correct answer. This understanding hinges on recognizing how temperature variations from the standard atmosphere affect the temperature reading at a specific flight level.