Shares of the world's biggest planemaker have fallen nearly 15% since the fatal crash of an Ethiopian Airlines 737 MAX jet in March, erasing about $40 billion in market value.

The stock has also been among the worst performers on the S&P 500 index and the Dow Jones Industrial Average. The benchmark index is up about 3% during the same period, while the Dow has risen by a marginal 0.2%.

"The dialogue is shifting more towards when the aircraft can get back into service as opposed to if," Morgan Stanley analyst Rajeev Lalwani wrote in a note.

"With shares down about 20% from their recent highs ... and the risk-reward skewing more favorably, we are comfortable with our "overweight" rating and price target of $500."

If the aircraft is cleared to fly by June, its operators, including Southwest Airlines Co, American Airlines Group Inc and United Continental Holdings Inc, would likely not have to extend costly cancellations that they have already put in place for the peak summer flying season.

(Reporting by Ankit Ajmera and Sanjana Shivdas in Bengaluru; Editing by Anil D'Silva)