Tutorial

6. Altitude Check
Altitudes are also described in a specific way. An altitude of 3,000 feet is spoken as you would expect, "three thousand feet." However, an altitude of 10,000 feet is spoken as "one - zero thousand feet." An altitude of 15,500 feet would be "one - five - thousand - five hundred feet".

At altitudes 18,000 feet and above, aircraft altimeters are set to 29.92 inches of mercury, the standard barometric pressure. These indicated altitudes are identified as Flight Levels (FL) and are measured in hundreds of feet. It is simpler than it sounds. An aircraft at Flight Level three - three - zero (FL330) has a barometric indicated altitude of 33,000 feet. Let's say a pilot requests to ascend to a higher altitude while en route. A possible response from the controller could be, "Affirmative, Speedy Flight one - niner - three. Ascend and maintain flight level two - six - zero."