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Flights from Islip to St. Louis

Find the cheapest flight options from Islip to St. Louis over the next three months. Book one-way tickets from SGD 100 and round-trip tickets from SGD 186.

      • ISP 20:29
        27h 4m
        1 stop
        STL 22:33
        Islip - St. Louis | Fri, Dec 12 | Frontier Airlines
        STL 15:30
        27h 4m
        1 stop
        ISP 19:34
        St. Louis - Islip | Mon, Dec 15 | Frontier Airlines
        SGD 186 SGD 1,666
        89% OFF
        89% OFF
        SGD 1,666 SGD 186
      • ISP 13:27
        10h 6m
        1 stop
        STL 22:33
        Islip - St. Louis | Fri, Dec 19 | Frontier Airlines
        STL 10:40
        8h
        1 stop
        ISP 19:40
        St. Louis - Islip | Mon, Dec 22 | Frontier Airlines
        SGD 376 SGD 1,666
        77% OFF
        77% OFF
        SGD 1,666 SGD 376
      • ISP 20:29
        27h 4m
        1 stop
        STL 22:33
        Islip - St. Louis | Tue, Dec 16 | Frontier Airlines
        STL 16:27
        26h 13m
        1 stop
        ISP 19:40
        St. Louis - Islip | Sat, Dec 20 | Frontier Airlines
        SGD 396 SGD 1,666
        76% OFF
        76% OFF
        SGD 1,666 SGD 396
      • ISP 10:45
        12h 48m
        1 stop
        STL 22:33
        Islip - St. Louis | Tue, Dec 16 | Jetblue Airways
        STL 16:27
        16h 34m
        1 stop
        ISP 10:01
        St. Louis - Islip | Sat, Dec 20 | Frontier Airlines
        SGD 507
        70% OFF
        SGD 1,666 SGD 507
      • ISP 12:20
        11h 13m
        1 stop
        STL 22:33
        Islip - St. Louis | Tue, Dec 23 | Frontier Airlines
        STL 16:27
        19h 42m
        1 stop
        ISP 13:09
        St. Louis - Islip | Sat, Dec 27 | Frontier Airlines
        SGD 856
        49% OFF
        SGD 1,666 SGD 856
      • ISP 10:46
        12h 47m
        1 stop
        STL 22:33
        Islip - St. Louis | Tue, Dec 23 | Jetblue Airways
        STL 16:27
        16h 34m
        1 stop
        ISP 10:01
        St. Louis - Islip | Sat, Dec 27 | Frontier Airlines
        SGD 1,216
        27% OFF
        SGD 1,666 SGD 1,216
      • ISP 13:00
        17h 25m
        1 stop
        STL Invalid Date
        Islip - St. Louis | Sun, Dec 14 | Normal Airline
        STL 15:00
        6h
        Direct
        ISP 16:00
        St. Louis - Islip | Tue, Dec 16 | Normal Airline
        Find More Flights
        Find More Flights
      • ISP 15:34
        7h 59m
        1 stop
        STL 22:33
        Islip - St. Louis | Fri, Jan 9 | Frontier Airlines
        SGD 100 SGD 625
        84% OFF
        84% OFF
        SGD 625 SGD 100
      • ISP 20:54
        27h 39m
        1 stop
        STL 23:33
        Islip - St. Louis | Mon, Jan 19 | Frontier Airlines
        SGD 114 SGD 625
        82% OFF
        82% OFF
        SGD 625 SGD 114
      • ISP 20:29
        27h 4m
        1 stop
        STL 22:33
        Islip - St. Louis | Tue, Dec 16 | Frontier Airlines
        SGD 128 SGD 625
        80% OFF
        80% OFF
        SGD 625 SGD 128
      • ISP 10:00
        14h 33m
        1 stop
        STL 23:33
        Islip - St. Louis | Tue, Jan 27 | Jetblue Airways
        SGD 160
        74% OFF
        SGD 625 SGD 160
      • ISP 10:00
        13h 33m
        1 stop
        STL 22:33
        Islip - St. Louis | Mon, Jan 12 | Jetblue Airways
        SGD 174
        72% OFF
        SGD 625 SGD 174
      • ISP 16:40
        19h 16m
        1 stop
        STL 10:56
        Islip - St. Louis | Mon, Dec 22 | Frontier Airlines
        SGD 200
        68% OFF
        SGD 625 SGD 200
      • ISP 21:09
        12h 36m
        1 stop
        STL 08:45
        Islip - St. Louis | Sat, Dec 13 | Frontier Airlines
        SGD 225
        64% OFF
        SGD 625 SGD 225
      • ISP 10:45
        12h 48m
        1 stop
        STL 22:33
        Islip - St. Louis | Tue, Dec 16 | Jetblue Airways
        SGD 231
        63% OFF
        SGD 625 SGD 231
      • ISP 14:04
        20h 41m
        1 stop
        STL 09:45
        Islip - St. Louis | Sun, Dec 21 | Frontier Airlines
        SGD 249
        60% OFF
        SGD 625 SGD 249
      • ISP 10:45
        23h
        1 stop
        STL 08:45
        Islip - St. Louis | Sat, Dec 13 | Jetblue Airways
        SGD 456
        27% OFF
        SGD 625 SGD 456
      • ISP 13:00
        17h 25m
        1 stop
        STL Invalid Date
        Islip - St. Louis | Sun, Dec 14 | Normal Airline
        Find More Flights
        Find More Flights

Displayed flight fares from Islip to St. Louis are based on average prices across airlines for the next 3 months, according to the latest Trip.com database.

Flight details for Islip to St. Louis

The distance between Islip and St. Louis is 1,478.87 km. Based on Trip.com's data, travel demand peaks in September. The off-season for travel is October.

Cheapest one-way flight priceSGD 100
Cheapest round-trip ticket priceSGD 186
Off-season for travelOctober
Peak season for travelSeptember
Flight distance1,478.87 km

Find the best time to fly from Islip to St. Louis

The cheapest time for Islip to St. Louis flights: Jan 4 to Jan 11 — one way flight prices from SGD 100.

Cheapest flights
From price
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  • 714
  • 1421
  • 2128

  • Jan

    284
  • 411
  • 1118
  • 1825

  • Feb

    251
  • 18
  • 815
  • 1522

  • Mar

    221
Displayed fare trends are based on Trip.com's aggregated average of the lowest flight prices from Islip to St. Louis, calculated over the upcoming 10 weeks.

Flight FAQs

  • What are the cheapest flights from Islip to St. Louis (ISP-STL)?

    Based on Trip.com data, Frontier Airlines offers one-way fares as low as SGD 100 on Cheapest nonstop routes (e.g. ISP to STL on Fri, Jan 9), while Frontier Airlines offers Cheapest nonstop round-trips from SGD 186 departing on Fri, Dec 12 and returning on Mon, Dec 15.
  • By analyzing data from all airlines on the Trip.com flight calendar, it looks like the best time to book a flight from Islip to St. Louis is around 40 days (6 weeks) in advance, and the best time to fly is usually on Tuesday, Wednesday, and Saturday. Tuesday typically offers the cheapest flights for departure, while Saturday offers the best return deals.
  • To find best deals on flights from Islip to St. Louis, you can use various tools on Trip.com:
    · Be flexible with your travel dates to get the cheapest flight deal. Now the cheapest flight deal is on Fri, Jan 9, with one-way flights priced at just SGD 100.
    · Compare airlines strategically. Budget carriers often provide the lowest base fares, while we found the most affordable airline currently operating on this route is Frontier Airlines.
    · Set up price alerts to easily monitor ticket prices without having to check every day.
    · Check Trip.com flight deals and promo codes frequently.
    · Avoid peak season unless you book very early. It seems the peak season for St. Louis travel is around September.
    · Get exclusive promo codes for Trip.com app users.
  • The cheapest months to fly from Islip to St. Louis is October, when demand for travel is lower.
  • After crunching the numbers on our December flight calendar, it's currently cheapest to fly from Islip to St. Louis on December 12, 2025 with Frontier Airlines, with prices starting at SGD 185.
  • The time difference between St. Louis and Islip is 1h.
  • Tickets can only be changed or canceled if permitted by airline policy. To submit a change or cancellation request, go to the flight bookings page, select the option to change or cancel your booking, choose the relevant passengers and segment, and submit a request. Please note that additional charges may apply according to the airline ticket policy. However, if the flight has been rescheduled and you would like to change or cancel your ticket, you can submit an involuntary cancellation request. For more details about change and cancellation policies, please check the customer support pages.