Is biofuel the answer to aviation's soaring fuel bill as well as its carbon footprint? Not at the moment, it's not, it seems.
Kerry Reals' cover story feature in the 19 April issue of Flight International looks at the potential of algae to replace kerosene. Recent experimental flights have shown that - scientifically - there is little holding algae back. The problem is the usual one. Lack of investment in the algae farms needed to produce the alternative fuel means that supply is short and so prices are high.
At the moment, using algae-derived fuel would be commercial suicide for any airline.
Read Kerry Real's Green Wing blog for more on all matters aviation and environment.
The environment feature package also has a piece by David Learmount on efforts to create a European Single Sky. Almost everyone agrees we need a simplified airspace and we need it now. So what's holding it back. David explains.
And Stephen Trimble has an update on efforts by a most unlikely environmental champion to develop hydrotreated renewable jet fuel - the US Air Force.