How far is Los Angeles airport (LAX) from the LA Union Train Station?

It is 20 miles.

If you need transportation there is a FLYAWAY bus that runs between LAX and Union station every 30 minutes from 5:00 am to 11:00 pm.

its about 20 miles and yes the faster way is using the Flyway

from LAX to Union station, cost will be $4.00 in July

i say half hour with traffic

45 min to and hour.