Also swapping the crystals whilst airborne.
Yes, well, easy enough in a biggish aircraft, I imagine. Not so easy in a Prentice on route to Sharjah from UK decades ago, with a box of 80 crystals bought for the route. The prehistoric VHF, mounted right behind the pilot seat with a controller on the panel, had 4 channels (A, B, C, D), rarely enough for a complete flight. So "Contact TWR on...." often meant acknowledging, switch radio off, find crystal for TWR frequency, reach behind seat, feel for the crystal in the channel to be changed, pull it out, push in replacement, unplug aerial feeder from set, also by feel, plug in bit of wire with bulb on the end, switch on, use left hand to transmit, right hand to twiddle the aerial tuner for max light, pull out wire with bulb on it, replace aerial feeder, call TWR. By definition, this often took place while on final approach, enough time in a Prentice at approach speed if started 1-2 miles out or before, but the aircraft still had to be flown while all this was going on. ATCOs were sometimes insensitive enough to comment adversely, even rudely about the delay, and occasionally seemed unable to understand and accept the explanation that changing crystals takes time and patience.
I've always thought that simply pushing buttons to select a new frequency is for sissies.