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KALN → KDECOpen in the mapper
ROUTE DISTANCE

Alton/St Louis to DecaturKALN → KDEC

St Louis Regional Airport (KALN / ALN) in Alton/St Louis, United States to Decatur Airport (KDEC / DEC) in Decatur, United States is 79 nautical miles — 146 kilometres, or 91 statute miles — on the great circle, on an initial bearing of 044°. A business jet at Mach 0.85 and FL410 takes about 0h 40m block time in still air.

Published by Overfly · Airport data: OurAirports, · Last updated

NAUTICAL MILES
79
KILOMETRES
146
STATUTE MILES
91
INITIAL BEARING
044°
BLOCK TIME
0h 40m
M0.85 · FL410 · still air

Can the aeroplane make it?

Range here is usable range — book range at long-range cruise, less a reserve allowance. It is the figure that decides whether the leg closes, and it is the question most mappers do not answer.

G650ER7,300 nm usable · 1%clears
G5506,550 nm usable · 1%clears
Global 75007,500 nm usable · 1%clears
Falcon 8X6,250 nm usable · 1%clears
Falcon 7X5,750 nm usable · 1%clears
Challenger 3503,000 nm usable · 3%clears
A350-9008,250 nm usable · 1%clears
B777-300ER7,120 nm usable · 1%clears
A320neo3,150 nm usable · 3%clears
A3203,150 nm usable · 3%clears
B737 MAX 83,250 nm usable · 2%clears
B737-8002,850 nm usable · 3%clears
An-1242,950 nm usable · 3%clears
Concorde3,650 nm usable · 2%clears
King Air 2001,400 nm usable · 6%clears
ATR 721,300 nm usable · 6%clears
Dash 8 Q4001,100 nm usable · 7%clears

How far from an airport?

Nowhere on the great circle is more than 13 minutes from a suitable airport at the one-engine diversion speed Overfly uses (430 kt in still air), so a twin-engine aircraft flies it under the 60-minute rule, with no ETOPS approval needed.

A suitable airport here is one OurAirports classes as large with a runway of 8,000 ft or more. An operator’s real alternates also depend on weather, fire cover and approval, and its diversion speed on the type. More in equal-time points and ETOPS, explained.

The two fields

KALN / ALN
St Louis Regional Airport
Alton/St Louis, Illinois, United States38.8903, -90.0460166 m · 544 ft elevationlongest runway 11/29 · 2,469 m
KDEC / DEC
Decatur Airport
Decatur, Illinois, United States39.8346, -88.8657208 m · 682 ft elevationlongest runway 06/24 · 2,590 m

Questions people ask about this route

How far is it from Alton/St Louis (KALN) to Decatur (KDEC)?

79 nautical miles. That is 146 kilometres or 91 statute miles, measured as a great circle between St Louis Regional Airport and Decatur Airport.

How long is the flight from Alton/St Louis to Decatur?

About 0h 40m block time for a business jet cruising at Mach 0.85 at FL410 in still air, including 30 minutes of taxi, climb and descent. Wind moves that figure in either direction — eastbound across the North Atlantic or the Pacific it can be an hour or more. This page is deliberately still-air so the figure is stable and citable; to apply the month's average upper winds from NOAA, open the route in the mapper and switch on seasonal winds.

What is the initial bearing from Alton/St Louis (KALN) to Decatur (KDEC)?

044° true at the departure point. A great circle changes heading continuously, so this is the initial bearing, not a constant one.

Which aircraft can fly Alton/St Louis to Decatur non-stop?

Of the types Overfly carries, G650ER, G550, Global 7500, Falcon 8X, Falcon 7X, Challenger 350, A350-900, B777-300ER, A320neo, A320, B737 MAX 8, B737-800, An-124, Concorde, King Air 200, ATR 72, Dash 8 Q400 clear it on usable range — that is book range less a reserve allowance.

Check it against your own aircraft
Open the route in the mapper to set cruise, flight level and reserve, edit the schedule, and add legs.
Open KALN → KDEC
NEARBY ROUTES

For reference and planning interest. Not for operational flight planning. Distances are great circle on a sphere from WGS-84 coordinates; block times assume still air. © 2026 Overfly.Flights