The missing 'I'

I got my boarding pass for my connecting flight from Frankfurt to Mexico at Chennai itself. I had a look and both the boarding passes in my hand, just to see where I'm gonna sit, cauz I had requested for an aisle seat. For the first flight the seat was 51D & for the second one it was 49K. Given that there are a total of 10 seats in a row in the economy class of a Lufthansa Boing (some model) plane, I got that for the first flight the seat is actually an aisle seat. A, B, C & then D ... ok its an aisle seat. Now I started counting for the second flight. A,B,C,D,E,F,G,H,I & then J. That sums up to 10. But the seat allotted to me as 49K. How is this possible? I counted the sequence again in my head, at least 3 more times, just to be sure. But each time, to my surprise, it ended at J.

I thought of going back to the counter and asking the guy if there was some mistake. But then I thought maybe this is the row at the end or something where they do actually have an "K" labeled seat. I got into my first flight and thought of searching for 49K before finding out my actual seat. As I boarded the plane and reached the economy class, I realized that they don't actually have an "I" seat. The sequence is - A,B,C,D,E,F,G,H,J & then K. The "I" was missing. I had been traveling by the same airline, by the same plane, for the past 8 times. I was amazed that how come I never noticed this before.

Did anyone of you know about this missing "I"? Is it only in Lufthansa or they ate it up in other airlines too?