https://en.wikipedia.org/wiki/Atmosphere_of_Mars

The <a href="https://en.wikipedia.org/wiki/Atmospheric_pressure" title="Atmospheric pressure" style="color: rgb(11, 0, 128); background-image: none; font-family: sans-serif; font-size: 14px;">atmospheric pressure</a> on the Martian surface averages 600 <a href="https://en.wikipedia.org/wiki/Pascal_(unit)" title="Pascal (unit)" style="color: rgb(11, 0, 128); background-image: none; font-family: sans-serif; font-size: 14px;">pascals</a> (0.087 <a href="https://en.wikipedia.org/wiki/Pounds_per_square_inch" title="Pounds per square inch" style="color: rgb(11, 0, 128); background-image: none; font-family: sans-serif; font-size: 14px;">psi</a>), about 0.6% of Earth's mean sea level pressure of 101.3 kilopascals (14.69 psi)

http://www.calctool.org/CALC/phys/default/pres_at_alt

I get a pressure of about 0.006 atmospheres at 36,000 meters. 

So, flying near the surface on Mars is about the same as flying at an altitude of 36,000 meters on Earth.

http://www.physlink.com/education/askexperts/ae610.cfm

says that altitude record for an airplane was 85,135 feet = 26,000 meters.