.74 is a mach reference.

The cruise speed in an Airbus is generated by a computer based on a 'cost index' number. These numbers can range from 0 to into the hundreds [I seem to remember entering 999 at some point, but I'd never admit to it!]. The cost index number is supposed to balance fuel economy with other non-fuel costs associated with the flight… crew costs, engine per hour costs, misconnected passengers, headwinds or tailwinds, etc. Near as I can tell, most Airbus operators use cost indexes of somewhere in the teens up to around 75. Frontier consistently uses a cost index of 4… which can lead to some very low cruise airspeeds.

I would guess that most operators fly their A320 series aircraft at somewhere around .78 mach. Frontier is usually .76 +/- .01 unless we're at lower altitudes for whatever reason and then it gets stupid slow. Hence the reference to being passed by birds in flight or by an A380.