Medium Large Transport; Low Wing; 2 Turbojet Eng
Flight Crew Air Transport Pilot (ATP)
Flight Crew Last 90 Days 176
Human-Machine Interface; Confusion; Communication Breakdown
ATC Issue All Types; Deviation - Track / Heading All Types; Deviation / Discrepancy - Procedural Clearance
Air Traffic Control Issued New Clearance; Flight Crew Became Reoriented; Flight Crew Returned To Clearance
Aircraft; Airspace Structure; Human Factors; Procedure
During preflight; non-standard flight plan; Captain retrieved and typed in fixes from PDC while I wasn't there.  When I returned I looked at PDC and then briefed the routing as Captain QC'd [quality checked/controlled] the fixes in the box.  Phonetically called out fix HRTUN (HURTIN). Captain had misspelled it as HURTN.  Center cleared us direct HRTUN. I pulled up the fix to top of the page; we confirmed it; and selected it.  A couple of minutes later; ATC queried our heading.  We confirmed direct HRTUN; he spelled it out phonetically; and that's when we caught it.  Put in the right fix and adjusted the heading about 20 degrees.  The headings were fairly close at that distance; two fixes that phonetically sound the same; with a letter shift difference. Recommend changing HRTUN or HURTN to something different.  Both in same geographic area and are less than 100 miles apart.  Continue QC checks of points and hard look at points on both flight plan and FMC.  This one was hard to catch with same letters and slightly different order.
Airline flight crew was advised of a track deviation in flight while navigation to HRTUN intersection and realized HURTN had been programmed during preflight. The waypoints are less than 100 NM apart.