Final answer:
The letter "L" in the airport data indicates the type of runway at the airport.
Step-by-step explanation:
In the airport data "450 L 51 122.7," the letter "L" indicates the type of runway at the airport.
In aviation, runways are categorized with letters to indicate their direction and magnetic orientation.
For example, a runway with an "L" designation could indicate that it runs from east to west or vice versa.