[Updated on October 14 to include additional information from Superjet and CityJet]

Irish regional airline CityJet announced Tuesday at the ERA General Assembly in Berlin that it has signed an agreement with Sukhoi Civil Aircraft (SCAC) and Superjet International (SJI) covering a firm order for 15 Sukhoi Superjets, along with options on a further 10.

Cityjet, which became independent from previous shareholder Air France Group when Germany’s Intro Aviation took control of the Irish regional last year, plans to lease the aircraft from an as-yet unnamed lessor. According to Superjet International, the deal is all but complete and it appears that the transactions tie closely together.

Sukhoi values the Cityjet agreement at more than $1 billion, including options and services. It expects to deliver the first of the 98-seat SSJ100s (the only five-abreast regional aircraft) in the first quarter of next year.

CityJet has agreed to take four of the airplanes in 2016 and 11 more in 2017. According to CityJet chairman Pat Byrne, one aircraft will arrive in February or March 2016, a second in May or June and two in July and/or August. “We then plan to take one a month in 2017” up until November, he said.

As the second major Superjet contract with a Western customer and the first in Europe outside the CIS, the deal represents a major accomplishment for SCAC and particularly SJI, Sukhoi’s Western sales and support arm for the SSJ100. Mexico’s Interjet remains the model’s only Western operator–and the largest operator of the type.

Cityjet plans to use the SSJ100 as the replacement for its fleet of Avro RJ85s, which it operates throughout Europe, including at London City Airport. Sukhoi said it expects the SSJ100 to gain the necessary certification for London City operations by the end of 2016.

According to Byrne, the airline plans to operate its Superjets in charter service next year, then introduce them into its London City route network in 2017.

 “We’re in a major transformation,” said Byrne. “We operate a fleet of 18 [Avro] RJ-85s but [the SSJ100s] will be our fleet replacement and will become our core fleet. We’ve been looking at this aircraft for quite a while, and we’ve been involved in a very extensive evaluation.

Questioned about the certification of the aircraft for the London City Airport, whose location in London’s Docklands close to the main financial district requires a steep approach, Superjet International CEO Nazario Cauceglia told reporters “the London City certification effort is well underway…it will be done by the end of 2016. It just requires a software change.”

Byrne said that Cityjet expects to operate its first four examples on routes other than London City, before switching them there in 2017. “We’re looking at a couple of opportunities out of Dublin, and we’re looking at Cork, and ACMI contracts for summer 2016,” he said.

Byrne and Cauceglia expressed confidence that other airlines will want to take a closer look at the aircraft and the ACMI contracts would provide them that opportunity.

Cauceglia identified Embraer as the other contender for the contract.

Meanwhile, Superjet continues to move towards European Aviation Safety Agency (EASA) certification of the higher gross weight variant of the aircraft, the SSJ100LR. The modification will allow the aircraft to fulfill its full range potential where required, said Cauceglia, bringing the figure up from 1,300 nm to 2,400 nm with a full passenger load through structure strengthening.

At present the variant has won certification only in Russia and the only operator remains Gaspromavia, which flies 10. Cauceglia expressed confidence that Belgian airline VLM, which previously showing interest in a deal through Ilyushin Finance, would return to negotiations. “I think that they will come back…I think that this deal will stimulate them very much,” he said.

He predicted that EASA would award the SSJ100LR certification in the first half of 2016 but hinted that he hoped it would be in place by the end of this year.