The easiest way to get to Sisteron from Calais is by using the autoroutes. The A26 runs to Reims and Troyes, then the A5 towards Langres and the A31 to Beaune. The A6 then leads to Villefranche (near Lyon) where the A46, by-passing the city, joins the A43 towards Chambery and then the A48 to Grenoble. The autoroute continues another 20km or so to the south of Grenoble and then the route nationale N75 may be used to reach Sisteron itself. The airfield lies to the north of Sisteron off the N85 and is signposted from the N75/A51 roundabout. Think 10-12 hours from Calais and you won't be far wrong.