There's also an option on the Extension code to specify Aircraft type:

AIRCRAFT aircraft1 aircraft2 AIRCRAFT T:737 C:PROP Allow flights on the listed equipment types (prefixed with T: ) or categories (prefixed with C: ). T:737 is the generic Boeing 737; more-specific variants may be specified (e.g. T:7M8 is the Boeing 737 Max8 variant). Categories include C:JET, C:TURBOPROP, C:PISTON, C:TRAIN, C:HELICOPTER, C:AMPHIBIAN, and C:SURFACE. This code may be negated to prohibit the listed aircraft types and categories.

So if you want to remove the annoying train options that can turn up you can use -AIRCRAFT C:TRAIN, so

ALLIANCE ONEWORLD; -AIRCRAFT C:TRAIN

would search Oneworld airlines but not trains (Madrid to Valencia you get a lot of train options)