Bombardier marked the start of the Farnborough air show by recording a conditional commitment from a yet-unidentified customer for five CSeries CS100s and 10 CS300s.

The order brings CSeries commitments to 153 aircraft from 13 customers, with the larger CS300 version, which can seat up to 149 passengers, slightly ahead in commitment totals; the CS300 has 82 orders in its backlog, and CS100 71.

The CSeries is planned to make its first flight before the end of this year, but difficulties in fly-by-wire software development that required additional work has left the manufacturer with no slack in this schedule, Bombardier Aerospace President Guy Hachey said in an interview.

Also, Bombardier has started assembly of components and fuselage sections, but has not yet entered into the aircraft final assembly process.

There also are questions regarding the readiness of the Chinese part of its supply chain. The first fatigue test unit is to be ready by September. Completing that work for the first flight test aircraft within four months is seen by many industry observers as unrealistic.