Haven't tested this but this is one way to go about it. Go to here:
https://github.com/DavidJClark/phpvms_5.5.x/blob/master/core/modules/PIREPS/PIREPS.php#L401
And change it to
$pilotid = $this->post->pilotid;
Note: The pilot you are entering for must have a bid already.
Here, https://github.com/DavidJClark/phpvms_5.5.x/blob/master/core/templates/pirep_new.php#L10
You would need to change this to something like this
<dd>
<select name="pilotid">
<option value="">Select a Pilot</option>
<?php
$allpilots = PilotData::getAllPilots();
foreach($allpilots as $pilot) {
echo '<option value="'.$pilot->pilotid.'">'.PilotData::getPilotCode($pilot->code, $pilot->pilotid).' - '.$pilot->firstname.' '.$pilot->lastname.'</option>';
}
?>
</select>
</dd>
You may also have to alter the FilePIREPForm() function a little.
This is answering the question, although I would recommend (if you have a lot of pilots) that you use a textbox and a JS AJAX request so that the list isn't really long and would require a lot of scrolling. Hope this helps in some way.
Edit: Looks like Yash got there first.