UPDATE 4-Boeing to submit 737 MAX software upgrade 'in the coming weeks'

WASHINGTON/SEATTLE, April 1 (Reuters) - Boeing Co said on Monday it planned to submit a proposed software enhancement package for the grounded 737 MAX in "the coming weeks" after the company had previously said it planned to deliver the fix for government approval by last week."We are working to demonstrate that we have identified and appropriately addressed all certification requirements and will be submitting for FAA review once completed in the coming weeks," Boeing said.More than 300 Boeing