MONTREAL — WestJet Encore has signed firm orders for six more Bombardier Q400 turboprops, eventually raising the Calgary-based regional carrier’s fleet to 36 aircraft.

The five planes plus another one booked in March are conversions of previously announced options valued at about US$200 million, based on list prices.

Encore is adding planes as WestJet’s Airlines Ltd.  expands the regional service to eastern Canada. The five planes will be delivered in 2016 and 2017.

Launched two years ago, Encore now has 114 daily departures to 24 cities in seven provinces.

The orders come as unions are reportedly trying to separately organize WestJet flight attendants and pilots ahead of federal unionization rule changes that come into force on Tuesday that would make it harder to form a union.

WestJet pilot and flight attendant associations recently signed five-year deals.

David Tyerman of Canaccord Genuity says he doesn’t expect a unionized workforce would significantly increase the airline’s costs but could reduce operating flexibility. It could also augment the threat of labour disruption, although Ottawa has shown that it is unwilling to permit strikes at rival Air Canada.

Bombardier also announced at the Paris Air Show on Monday that CSeries launch customer Swiss will switch 10 of its 30 firm orders to larger CS300 aircraft.

The Montreal-based aerospace manufacturer has commitments fro 603 CSeries aircraft, including 243 firm orders.