Some seat numbers missing on flight

[Raghav Gupta]

Why some row numbers like 13 ( know the reason of unlucky number), 18, 19, 20, 21, 32, 33 and 42 are missing on flights?

 

[Vanadium 50]

So that certain rows are standardized across the fleet - e..g. 20 and 21 are always exit rows, or that 11 is always the first row in economy.

This took Google less than a second to find.

 

[Raghav Gupta]

So that certain rows are standardized across the fleet - e..g. 20 and 21 are always exit rows, or that 11 is always the first row in economy.

This took Google less than a second to find.

I used google but was not able to find the answers. Maybe I don't know the correct keyword. I typed "Why certain rows are missing in flights". Got the only result of sites showing why 13 is omitted.
Why 18, 19 are omitted then?

 

[CWatters]

There are lots of reasons. Sometimes it's so that the same row numbers exists on two different models of aircraft. That helps when the airline has to swap out a plane. More..

http://edition.cnn.com/2011/TRAVEL/05/02/plane.row.numbers/

 

[Vanadium 50]

Why 18, 19 are omitted then?

Did you bother to even read what I wrote? "So that certain rows are standardized across the fleet".

 

[Silicon Waffle]

It's nice to learn that assigning a number to a seat on an airplane also needs to follow a certain standard.