In theory, yes. In practice, obstacles and terrain in the approach area may not allow it. Approaching in level flight would be equivalent to approaching a level runway on a 4.5 degree glideslope, i.e. still a steep approach requiring a greater flare height (relative to the runway) than a normal approach.
Vilas above expressed it perfectly in somewhat different words.
P.S.1
It should be obvious that I'm talking of the final stage of the approach to the runway.
P.S.2
Conversely (and perhaps less controversial), for landing on a downsloping runway, the PAPI should be steeper than for a level runway.
Last edited by Gysbreght; 9th May 2014 at 10:56.
Reason: P.S. 1&2