April 29 (Reuters) - Credit rating agency S&P on Monday

assigned a BBB- rating to new Boeing ( BA ) unsecured bonds,

confirming that the U.S. planemaker is looking to tap markets

after burning $3.93 billion of free cash flow during the first

quarter.

Boeing's ( BA ) credit rating faced pressure last week from rating

agencies after a January mid-air blowout of a cabin panel led

the planemaker to slow production of its best-selling jet.