excess fuel
Yes somewhere between 3% and 4% is correct. However if excess fuel is carried crews tend to waste the excess by not flying efficiently so the 3% becomes 6%. Eu Ops (JAR Ops) allows crew to land with really low fuel figures and stay legal. It is fine if the company has a robust fuel monotoring policy and not just rely on on board computers. (A330 out of fuel on the Atlantic comes to mind)
We regularly fly 6 hour + sectors on our Hawkers which means landing with 1000 lbs of fuel. This is fine and legal if the destination is good wx and close alternates. This is about 50 minutes of fuel. A lot of crews are initially wary of this. If so I ask them if they would be prepared to put 50 minutes of fuel in a cessna 150 and do a circuit and all say they would be happy to do that. I then point out that how come they are happy to TAKE OFF with 50 mins of fuel but not LAND with that amount!!
It all comes down to the fact that some crews worry that the 50 minutes of planned arrival fuel will somehow disappear during the flight. As long as crews know their aircraft, power settings and fuel flows the 50 minutes always stays on board as long as a good flight plan system has been used (Jet Plan is brilliant and accurate to 1%). The trick is to convert that 50 minutes into 60 or 70!! It makes a 6 hour sector slip away and for those who are prepared to take the effort it makes the difference between a pilot and a professional.
On another note, my company does not allow "refuelling on the guages" but on known arrival fuel plus uplift. This is also new to a lot of pilot, but I have not run out of fuel yet!