WASHINGTON--By the end of 1941 the United States will have a land-based air force capable of a strong defense against attack on the Western Hemisphere, well-informed Congressional sources said tonight.

They disclosed that the crucial period in adequate aid defense is between now and late fall. After that the supply and production of planes will be great enough to insure control of the air over both North and South America.

These sources, basing their statements on Army and Air Corps figures disclosed that the Army is now and for

several months has been getting quantity delivery of combat planes second to none in quality. The actual delivery figures are a military secret