Ask Captain Lim

Dear Captain Lim,

I live in an area where I can see jets with vapor for quite some time. It appears that the flights are cross country and as such are at maximum heights.

It is possible for me to observe a flight for more than four minutes?

Can you help me determine how much ground mileage is covered if I use a stop watch when I first observe the plane and when I stop the watch after I can no longer see it?

Thanks for your help and your web site is sharp.

Frank,
Aged 65, and new to the computer

Hi Frank,

The proper name for the vapor created by the jets is known as contrail or condensation trail. (See here).

Of course, you can observe the jet with the contrail for more than 4 minutes if the environmental conditions in the clear sky are present.

You can also determine how much mileage is covered by using your stop watch if only you know the jetliner that is creating the contrail.

As a rule of thumb, the following 4 planes can fly at these speeds:-

Boeing 747 - 8.5 miles per minute
Boeing 777 - 8.4 miles per minute
Airbus A330 - 8.2 miles per minute
Airbus A320 ?-7.8 miles per minute

So, a Boeing 747 will cover 34 (8.5 x 4) nautical miles in four minutes if you could precisely time the duration of the vapor. Those 34 "ground" mileages (nautical miles) would be the length of the so-called "vapor trail".

Again, if you could record another contrail created by an Airbus A330 as 10 minutes, the contrail would be 82 (8.2 X 10) nautical miles long.

Have fun chasing the contrails! :-)