Can't help you there, I live a couple of miles from the airfield. Downstairs a Sony Air 7 will pick up what the pilots are saying, upstairs on a good day it'll just about get the tower as well.
If your scanner has a removable aerial, it's probably connected with a BNC connector (round, requires about 1/4 turn anticlockwise to twist loose). If that's the case, it's fairly easy to make a really good antenna - technically called a dipole - yourselves.
Get hold of a sufficient length of "RG-58" wire. Usually black, this was used a decade ago as "thin ethernet" or plainly "ethernet" to network computers together. Any computer shop/techie with a sense of nostalgia will have miles of the stuff lying around doing nothing (I know I do). One end simply twists onto the scanner. From the other end, snip the connector off, and either splice out the core from the mantle, or use some fasteners to connect it to suitable lengths of household electricity wire. In any case, the core (or the wire fastened to it) should be vertical, pointing downwards, and the mantle (or the wire fastened to it) should be vertical, pointing upwards (or the other way around, it doesn't matter.
What does matter is the length of the vertical bits: 1/4 of the wavelength in the middle of the frequency band you're trying to monitor. For airband, that works out to about 59 cm.
Hang the antenna in the attic as high as you can, using only non-metallic components. Mine is attached with plastic tie-wraps to a piece of wooden floor trimming, then fastened with some velcro to a vertical roof support beam.
I can pick up all ground traffic, even the departure ATIS, from Schiphol airport which is about 10 miles away, and everything in the air for hundreds of miles around. Good sound quality too - much, much better than the tiny whip antenna my scanner came with.
Took me about 30 minutes to put together.