Richard Mountain's legs were too long for the aisle seat he was given on a Hong Kong Airlines flight to Auckland. Photo: Supplied

A Hong Kong Airlines passenger says he is furious and will complain to the airline after he was charged $100 to "upgrade" from one economy seat to another with more leg room.

At 1.98 metres tall [6ft 6in], Richard Mountain, from Dunedin, needs plenty of leg space so when he checked into the Hong Kong Airlines flight in Hong Kong yesterday he requested extra room.

Mountain said he was assured he would be seated in a row with extra space but instead he was given an ordinary aisle seat and his legs were stuck across the aisle.

"They put us at the back of a section so that I couldn't put the seat back easily and I couldn't fit in," Mountain said.

"My legs were in the aisle which is actually an aviation hazard because the aisle was completely blocked."

Mountain, who had been holidaying in Thailand with his girlfriend said the hostess tripped over his legs three times before take-off.

"She banged my knee quite hard and I complained and asked if I could move. I asked them how are they going to get the trolley past and she said I'd have to stand up and move each time."

The row of four empty seats on a Hong Kong Airlines flight that a passenger had to pay $100 to upgrade to from another economy seat. Photo: Supplied

In the section immediately behind Mountain was a front row of four empty seats where there was more leg room because there were no seats immediately in front.

"They said 'We're not upgrading you for free. You've got to pay'. I ended up having to pay $100 New Zealand dollars to sit in a seat which would otherwise be unoccupied."

The 34-year-old from Dunedin said he complained to no avail so he paid the fee.

"I always get extended leg room for free. I've been to 35 countries, over 200 flights in my life and I've never been asked for money for sitting somewhere I can fit in.

"But to charge me extra money for being tall, It was an absolute disgrace."

Mountain said he would write to the airline and make a formal complaint.

"I'd like my $100 back."

The Herald has contacted Hong Kong Airlines for a response.