Brazilian regional jet Embraer 175 is making more inroads into the U.S. commercial aviation market, apparently at the expense of aircraft made by North American manufacturers.

United Airlines said it is adding 30 new Embraer 175 aircraft to its United Express fleet under contracts signed last year because the jets are comfortable and fuel-efficient.

The airline group said it will introduce the Embraer 175 commuter jet on two key routes in May. The new aircraft are to be operated by United partner SkyWest Airlines and will start services between Chicago's O'Hare Airport and Ronald Reagan Washington National Airport and between O'Hare and Boston's Logan International airport.

The Chicago-Washington service is due to start May 17 and flights to and from Boston will start two days later.

United called the Embraer 175 an ideal aircraft for high-frequency business travel routes because they provide passengers with wider seats and aisles and larger overhead capacity for larger carry-on bags.

SkyWest announced last year it would buy $4 billion of Embraer jets and United revealed plans to buy Embraer jets for $840 million.

The orders were placed after United and SkyWest reached understandings that SkyWest would operate all the E175s in both fleets but under the United Express brand. The purchase is seen by the commercial aviation industry as part of a growing trend toward aircraft that are cheaper to fly and allow airlines to charge more. The E175 tops the list of fuel-efficient alternatives to aging aircraft seen as gas-guzzlers and increasingly more expensive to maintain.

"The 76-seat Embraer 175 is the newest addition to the United Express fleet," United said in a news release. "United Express carrier SkyWest Airlines will operate the flights, with 12 seats in United First, 16 seats in United Economy Plus and 48 seats in United Economy."

The airline emphasized passenger comfort and new features, including a power outlet for each seat in the first class area.

"Our customers tell us they value comfort and convenience in an in-flight experience," United Executive Vice President of Marketing Jeff Foland said in a statement. "The addition of the E175 to the United Express fleet enables us to maintain and better serve our customers, particularly in regional and in high-frequency business markets, as we build a flyer-friendly airline."

Industry reports said Embraer's rivals would struggle to catch up with the Brazilian manufacturer as it takes on planemakers and procurement agencies.

Embraer announced this month it plans to sell at least 1,500 regional jets in the Asia Pacific region over the next 20 years, a cumulative total of deals worth $70 billion at current list prices.

The Brazilian manufacturer says it has a 51 percent global market share in the regional jets category and has dominated 62 percent of deliveries over the last decade.

Embraer's forecast represents nearly 20 percent of the worldwide demand for the regional jets segment in the 20-year period. Only about 35 percent of the projected deliveries will be replacing aging aircraft and modernizing inventories in the Asia Pacific region, while 65 percent will represent expansion in regional passenger traffic, Embraer said in a statement. Comparable data for E175 sales expansion in North America are yet to be released.

Embraer's E-Jets family of narrow-body medium-range twin-engine jet airliners has logged more than 1,400 orders and more than 1,000 deliveries to date. The aircraft are in service with about 65 customers from 45 countries, Embraer says.