The route starts at Britannia Hut. It can be reached from Saas Fee on foot in 4h - either over Plattjen (nicer) or over Maste 4 - or from cablecar station Plattjen in 2h, or from cablecar station Felskinn in 45min.
This route and also the normal route to Strahlhorn have the same start as the route to Allalinhorn, but then leave soon the Hohlaubgletscher through col 3105 and descend a bit to Allalingletscher. Then they ascend on this glacier near Hohlaubgrat foot. To reach Fluchtpass, one has to leave the normal route and aim for the southern end of rocky island (3451) and further for Fluchtpass (3720). Most likely no trail will be available, you have to choose you own way.
The northeast ridge starts here - more precisely it's an east edge of the north flank. The slope has a lot of crevasses, in the first section entirely covered by snow (end of August). This section is ended by a steep ice wall which can be crossed by a less steep diagonal ledge leading to the right. Above it, we have encountered 2-3 big crevasses with snow bridges and used ice axe belay to cross them.
The default route holds on to the ridge, ascends side peak (4143), and then ascends the rock section (II) below the summit - this is the description from the guide. The crevasses and low visibility mislead us directly below the summit, and we ascended it directly through the steep snow slope (there were sections with ice only a few centimeters under surface in the end of August). This option is recommended only at the start of the season, Classification AD+, 40-50 degrees according to the guide. We descended via the normal route - a "highway" without any technical difficulties.
This is a route nr. 106+106a in the SAC guide "Walliser Alpen 5: Vom Strahlhorn zum Simplon" (1993 edition).
ice axe, crampons, rope; ice screws might be useful
photos from our trip