Did you know that Lufthansa doesn't have rows 13 and 17 on their planes?

United skips row 14 too. And sometimes even more. On recent flights, I've seen row numbering like 12-15-20, 12-20, and even 12-21. It depends on the specific aircraft model. The 12-15-20 numbering was on a Boeing 737, and 12-20 was on an Airbus 320.

Here you can find the entire company fleet with seating charts.

The reasons are the same old story: customer superstitions and the cheapest way to keep everyone happy. I doubt anyone would be afraid to fly in row 35. Though honestly, when it comes to planes, the safety in row 13 probably isn't much different from rows 12 and 14.