Surface access is incredibly important to MAN. Bringing people within shorter catchments to the Airport makes it more likely they will use it.
Take the A556 which opened at the weekend. That will save people between 10 and 20 minutes getting to and from MAN. It could help make the mind up for someone in the potteries considering MAN or BHX or help MAN over LHR for someone in Birmingham.
It's not the be all and end all but it helps.
As will the A6 - Manchester Airport Relief Road (A6MARR) when that opens in 18 months time. As will the Ordsall Chord when it starts to take rail traffic. And so on and so forth......