PHOENIX, March 10 (Reuters) - Colombia's Avianca is ready to look at the Boeing 787-9 wide-body aircraft but has questions about its performance, its top aircraft buyer said on Tuesday.

"Boeing is trying to sell us the 787-9. We are analysing that option right now, but the performance is volatile," Jose Yunda, director of fleet management, said.

"If performance improves a little, we would like to take another look," he told a conference organised by the International Society of Transport Aircraft Trading (ISTAT).

United Airlines told the same gathering that the U.S. carrier was looking at both the Airbus A321LR, a long-range version of its largest narrowbody jet, and Boeing's studies for a possible jet between its single-aisle and twin-aisle models.

"We are looking at both ... The A321LR looks pretty decent, but we will see what Boeing is going to do in the mid-market," he told the ISTAT conference.

He declined further comment.

(Reporting by Tim Hepher; Editing by Chris Reese)