Ten years ago, the emergence of the regional jet evoked a degree of dismay among airspace and air traffic planners who forecast that, by replacing turboprops, these 50-seat upstarts would be barging in on already-congested cruise altitudes and causing havoc.

Except it didn't quite work out that way. Despite their popularity, regional jets haven't jammed the airways, at least not to the extent feared, and have gradually nestled into the air transport network without creating too much of a stir.

But now that sense of mild dread seems to be descending again over the very light jet phenomenon, enough to prompt Eurocontrol to take a close look at whether the VLJ threat is genuine.

Part of the concern about VLJs centres on potentially detrimental effects to en-route traffic flow. But while VLJs are rated to operate to 40,000ft (12,200m) and beyond, they will typically be used for short sectors, which - as with regional jets - tends to result in distribution at lower cruise altitudes than larger aircraft.

However, there are other reasons why Eurocontrol is trying to get a grip on the issue. VLJs will address not only the current business-jet sector, but will also generate new business models based on air-taxi services. Although the European Business Aviation Association has dismissed gloomy suggestions of a sky "black with VLJs" and sees steady, rather than explosive, growth, VLJ market forecasts vary wildly. No one is really sure just how many aircraft will ultimately be zipping across the continent. That's a bad start when you're trying to work out how to cope.

Speed and climb performance - brought up when regional jets were the latest craze - have returned with the VLJ. But VLJs have also brought their own batch of safety issues. They're light, by definition, and that means paying attention to wake and separation considerations. And unlike regional jets, VLJs are not subject to European collision-avoidance system (ACAS II) requirements. Common sense, and the notorious crowding of core European airspace, might prompt every VLJ operator to fit ACAS II without a revised Eurocontrol mandate. But don't bank on it.

Source: Flight International