Article doesn’t match headline. Flying at 1,500 meters is very different from losing 1,500 meters.
Flying at 1,500 meters burns a lot of fuel, and even more getting back up to altitude.
If they flew at 1,500 meters for even 30 minutes, it shortens their range.
You avoid secondary radar by turning off the transponder.
You avoid primary radar with maneuvers.
There are 2,000 meter mountains on Malaysia, iirc.
You avoid primary radar with maneuvers.