Er.... Mach is unitless? Mach 1 equals a specific speed at sea level, which happens to be the speed of sound at sea level. Depending on teperature, the speed of sound at sea level is about 776 miles per hour. This changes as you change altitude, so Mach 1 at 60000 feet is different than Mach 1 at 0 feet.
Also, concerning the matter of escape velocity, you simply must have more energy than gravity. Here's one website for that: Escape Velocity
The reason why jets can't leave the atmosphere is because they require air (duh!), and currently, you need a rocket to supply enough thrust long enough to leave Earth. To lift a Jet into space requires much less thrust than a space shuttle.
that is where i come in, remmeber GMm/r? ( i am going to be an engineer by the way) if u luanch an aircraft form a high place; for my case of saying that u dun nescessary need that 11km/sec to get out of earth; i will chose first everest.
hieght of everest = 8850m
radius of earth = 6378136 m
Grav constant(top of my head) = 6.67259E-11
M earth = 6E24 kg
m = canceled
(1/2)mv^2 = GMm/®
for surface of earth
v = 11204m/s
if R = Rearth + Reverst
v = 11196.69m/s
if R = (Rearth + RSr71(assume 20km)
v = 11186.93m/s
now applying to aero space, we should check the fundemental methold which the constant escape velocity is calculated from. it is a energy type calculation thus it assumes that no energy will enter the system once the system is set in motion (just like a bullet out of a gun, once the bullet is out of the barrel nothing is pushing it cept the restive air flow). but a rocket is constantly supplying energy along the process. and also when fuel is burnt the m of the rocket~ decreases so therefore it is capable of reaching space without going 11km/sec iirc the space shuttle and apollo series do not even reach that speed untill the very end of the launch. and that is only because they are in space.
and mach num iirc is a ratio aka without a unit. (m/s)/(m/s) = 1