Embraer’s waning E-Jet backlog received a welcome boost this week with a firm order for 47 seventy-six-seat E175s from Indianapolis-based Republic Airways. The deal, announced Thursday morning, includes options on another 47 of the airplanes, potentially raising its list-price value to $4 billion.

The carrier plans to assign the airplanes to its Republic Airlines subsidiary, which, under a newly signed capacity purchase agreement (CPA), would fly them in the American Airlines regional network as American Eagle. Still under Chapter 11 bankruptcy protection, American expects to see the first of 53 Republic E175s enter its system in June. The CPA remains subject to bankruptcy court approval.

Along with the purchase agreement for 47 new aircraft, Republic has agreed to lease a previously owned E195 from Embraer and acquire another five used E175s from a third party. It expects to become the first airline to take delivery of Embraer’s so-called enhanced fuel performance E-Jets, featuring a new winglet design scheduled to enter flight testing this March or April.

Republic plans to place the dual-class jets into operation at a rate of some two to three per month through the first quarter of 2015. The CPA with American calls for each aircraft to operate as American Eagle for 12 years from its in-service date, extending the term of the agreement into 2027.