[mou] Flight call ID help

[Pastor Al Schirmacher]

While walking Milaca Hiking Trails this morning (central MN, for those not 
familiar with the booming metropolis of Milaca), observed a finch-sized bird 
with a single fly over call - "eeeet" to my ear - rather weak sounding - 
repeated once.  Did not observe any undulance in flight.  No color was 
observed against the white sky.  The call was similar to a Brown Creeper.

So I welcome input.  Only have Sibley with me here - he mentions a variant 
WW Crossbill call that is similar (could not discover same on net).  Two 
WW's were observed in this location last year.  However, is their flight 
pattern ever direct?

On the other hand, I probably would have simply "dismissed" this as a 
creeper - except for the observed fly over - since the dozens of creepers 
I've seen over the years are only observed ascending tree trunks or flying 
from tree to tree.  Imagine they fly over head at times, but has anyone 
observed same?

Am I missing something obvious?

Thanks!

Al Schirmacher
Princeton, MN
Mille Lacs & Sherburne Counties