Thepointsguy.com took a look at Allegiant's longest and shortest flights.
The longest was CVG – LAX at 1,900 miles
The shortest was FAT-LAS at 258 miles (also Allegiant's first route and the longest continuously operated route at Allegiant)
The full article is at
http://thepointsguy.com/news/longest-shortest-allegiant-air-flights/LongestCincinnati (CVG) – Los Angeles (LAX): 1,900 miles
Las Vegas (LAS) – Knoxville (TYS): 1,739 miles
Cincinnati (CVG) – Las Vegas (LAS): 1,678 miles
Grand Rapids, Michigan (GRR) – Las Vegas (LAS): 1,628 miles
Bismarck, North Dakota (BIS) – Orlando Sanford (SFB): 1,628 miles
Los Angeles (LAX) – Memphis (MEM): 1,619 miles
Mesa/Phoenix (IWA) – Traverse City, Michigan (TVC): 1,599 miles
Las Vegas (LAS) – South Bend, Indiana (SBN): 1,590 miles
Indianapolis (IND) – Las Vegas (LAS): 1,590 miles
Fort Wayne, Indiana (FWA) – Mesa/Phoenix (IWA): 1,562 miles
ShortestFresno (FAT) – Las Vegas (LAS): 258 miles
Mesa/Phoenix (IWA) – Las Vegas (LAS): 276 miles
Las Vegas (LAS) – Santa Maria, California (SMX): 309 miles
Las Vegas (LAS) – Reno (RNO): 345 miles
Las Vegas (LAS) – Stockton, California (SCK): 358 miles
Las Vegas (LAS) – Monterey, California (MRY): 375 miles
Knoxville (TYS) – Destin-Fort Walton Beach, Florida (VPS): 395 miles
Las Vegas (LAS) – Oakland (OAK): 407 miles
Grand Junction, Colorado (GJT) – Las Vegas (LAS): 413 miles
Asheville, North Carolina (AVL) – Baltimore (BWI): 414 miles