The Airbus A321 is a narrowbody jet with a single central aisle and up to 187 seats arranged according to the airline and version. For example, the US Airways version has eight pairs of first class seats and the American Airlines transcontinental plane has an additional 10 single flatbed seats.
In addition to four rows of first class seats, the US Airways A321 has 30 rows of economy seating arranged in groups of three, while the American Airlines version has six rows of extra seats and six rows of economy seating, arranged in threes. Both planes have restrooms at the front, back and to the center. SeatGuru.com shows the different seat plans for each airline.