Ukraine's Dniproavia is to introduce 10 Embraer 190 aircraft which it intends to operate in co-operation with partner AeroSvit.
The agreement also includes an option to acquire five additional twinjets.
Dniproavia has a Western-built fleet, the regional component of which comprises Embraer ERJ-145s.
The carrier, based in Dnipropetrovsk, will take the 190s under a lease structure which, says Embraer, will be "arranged by a third party".
But the airframer points out that the jets will be added to its firm order backlog, and values the agreement at $400 million - rising to $600 million if options are exercised.
The 190s will be fitted with 104 seats, in two classes, and the first two aircraft will be delivered in the fourth quarter of this year.
Dniproavia has tied up with local operators AeroSvit and Donbassaero under an alliance branded as the Ukrainian Aviation Group.
"Operating the Embraer 190 alongside our narrowbody aircraft will allow us to substantially expand our domestic and intra-European network," says Ukrainian Aviation Group executive secretary Vadim Shvitay.
Ukrainian carrier WindRose already uses the Embraer 195 in its operations.