Lufthansa unit Swiss International Air Lines Ltd. will decide whether to upgrade a further five Bombardier CSeries jets to the larger variant by the end of the year, the carrier’s chief executive said on Wednesday.

Swiss, the launch customer for the new plane, had placed a firm order for 30 CS100 jets and has already converted 15 of those to the larger CS300 variant.

“It’s still open, but I think it’s very probable that we will decide for the larger [CS300 Bombardier jet],” Swiss CEO Thomas Kluehr told Reuters on Wednesday at an event to unveil Swiss’s first CS100 plane.

Lufthansa also has an option for a further 30 CSeries jets, with the decision on whether to exercise those up to the Lufthansa executive board.

“It’s a wonderful aircraft, so I think the chances are good, but I don’t know when the final decision will be made,” Mr. Kluehr said.