For the second time in less than a year, Mesa Air Group [Nasdaq: MESA] has turned to the bond market to finance aircraft acquisitions.

The ninth largest U.S. regional airline earlier this month sold $100 million in 20-year convertible bonds. The company said it would use the proceeds for general corporate purposes and to fund future aircraft purchases.

The carrier recently decided to exercise options to buy 20 Bombardier [Toronto: BBDb] CRJ-700 and CRJ-900 models which will be used for United Airlines [OTC: UALAQ] and America West Airlines [NYSE: AWA]. That deal has been valued at $637 million. Mesa also agreed to purchase eight CRJ-200s to service its contract with US Airways [Nasdaq: UAIR].

Mesa in late January concluded a financing agreement, which will provide either interim or backup permanent financing for the next 35 regional jet deliveries.

In the latest bond sale, Mesa has structured the notes so that they can convert to stock at $14.45 per share - a 40.3 percent premium over the Feb. 4 closing price. The bonds will pay 3.625 percent interest on the notes for the first five years of the 20-year notes. At maturity, $171.4 million in accrued interest will be due.

The undisclosed buyer has until early March to purchase an additional $25 million in convertible bonds.

Last June, Mesa sold $100 million worth of convertible bonds due in 2023. These notes can be converted into common stock at $10 per share. The interest rate on the June bonds was set at 6.25 percent. The notes were also sold to finance aircraft purchases.