WORLD SITES TO FIND A GOOD TICKET
Not all sites can find everything.
Therefore categories below are mentioned as "1) FIND ALWAYS ALL" and "2) FIND ALMOST ALL".
As a test, routing had been used "Prague - Havana in dates 1.4.2023 - 30.4.23, which is not any super abandoned location, and therefore it should be processed by any ticket engine. But reality shows different results. Sites in option 2) find nothing from that. It means even for other routings; there could be a limitation up to the deal between the site and airlines or ticketing system (not all companies have all connections).
Another factor is the price of the ticket. It is listed from top to bottom, from cheapest to most expensive. This comparison was made by routing "Prague - Bangkok (BKK)" for the exact dates, 1.4.2023 - 30.4.2023, and as a flight for compassion had been used Emirates.
Finally, in the brackets in blue color is the cheapest price found on the site with any airline combinations between required points (here option Prague / Vienna) on the days +/- (simply the best option), if this solution was possible.
Emirates Price on Emirates web - 1.301 USD
0) REFERENCE
00) ITA Matrix
00) Skiplagged
00) Kiwi
00) Google Flights
1) FIND ALWAYS ALL
01) Student Agency = Kralovna - 0.903 $ - Student Agency // [0.928 $ - Oman Air]
02) Letenky - 0.909 $ - Student Agency // [0.792 $ - Air India from Vienna]
03) Letuska - 1.131 $ - Asiana // [n/a]
04) Pelikan - 1.176 $ - Pelikan // [0.805 $ - Air India from Vienna]
05) Jetcost - 1.217 $ - Lastminute // [n/a]
06) Skyscanner - 1.238 $ - Trip // [1.219 $ - Eurowings + Scooot + Qatar]
07) Dohop - 1.244 $ - ?? // [n/a]
08) GoToGate - 1.248 $ - Booking // [1.128 $ - Eurowings + Scooot + Qatar]
09) Jetradar - 1.254 $ - GoTravel // [n/a]
10) Opodo - 1.279 $ - eDreams // [n/a]
11) Google Flights - 1.286 $ - Alphabet // [1.116 $ - Eurowings + Scooot + Qatar]
12) Lastminute - 1.294 $ - Lastminute // [n/a]
13) eDreams - 1.295 $ - eDreams // [n/a]
14) seat24 - 1.297 $ ?? // [0.992 $ - Eurowings + Scooot + Qatar]
15) eSky - 1.302 $ - eSky // [n/a]
16) FlyHub - 1.563 $ - FlyHub // [n/a]
2) FIND ALMOST ALL
17) Kayak = Momondo - 1.294 - 1.262 - Booking // [1.209 $ - Eurowings + Scooot / Qatar]
18) Priceline = Cheapflights = Agoda - 1.262 - 1.296 $ - Booking // [n/a]
19) Travelocity = Hotwire = Orbitz = Cheaptickets - 1.262 $ - Expedia // [0.961 $ - Turkish + Oman Air / Oman Air + Qatar]
20) Expedia - 1.296 $ - Expedia // [n/a]
21) Cheapoair = Onetravel - 1.304 $ - TravelFare // [0.981 $ - Austrian + Eva Air]
22) Webjet - 1.367 $ - WebJet // [n/a]
3) OTHERS
23) Hopper
Conclusion
The best Direct Price
01) Student Agency = Kralovna - 0.903 $ - Student Agency // [0.928 $ - Oman Air]
02) Letenky - 0.909 $ - Student Agency // [0.792 $ - Air India from Vienna]
The best Combination Price
04) Pelikan - 1.176 $ - Pelikan // [0.805 $ - Air India from Vienna]
14) seat24 - 1.297 $ ?? // [0.992 $ - Eurowings + Scooot + Qatar]
19) Travelocity = Hotwire = Orbitz = Cheaptickets - 1.262 $ - Expedia // [0.961 $ - Turkish + Oman Air / Oman Air + Qatar]
21) Cheapoair = Onetravel - 1.304 $ - TravelFare // [0.981 $ - Austrian + Eva Air]
Not all sites can find everything.
Therefore categories below are mentioned as "1) FIND ALWAYS ALL" and "2) FIND ALMOST ALL".
As a test, routing had been used "Prague - Havana in dates 1.4.2023 - 30.4.23, which is not any super abandoned location, and therefore it should be processed by any ticket engine. But reality shows different results. Sites in option 2) find nothing from that. It means even for other routings; there could be a limitation up to the deal between the site and airlines or ticketing system (not all companies have all connections).
Another factor is the price of the ticket. It is listed from top to bottom, from cheapest to most expensive. This comparison was made by routing "Prague - Bangkok (BKK)" for the exact dates, 1.4.2023 - 30.4.2023, and as a flight for compassion had been used Emirates.
Finally, in the brackets in blue color is the cheapest price found on the site with any airline combinations between required points (here option Prague / Vienna) on the days +/- (simply the best option), if this solution was possible.
Emirates Price on Emirates web - 1.301 USD
0) REFERENCE
00) ITA Matrix
00) Skiplagged
00) Kiwi
00) Google Flights
1) FIND ALWAYS ALL
01) Student Agency = Kralovna - 0.903 $ - Student Agency // [0.928 $ - Oman Air]
02) Letenky - 0.909 $ - Student Agency // [0.792 $ - Air India from Vienna]
03) Letuska - 1.131 $ - Asiana // [n/a]
04) Pelikan - 1.176 $ - Pelikan // [0.805 $ - Air India from Vienna]
05) Jetcost - 1.217 $ - Lastminute // [n/a]
06) Skyscanner - 1.238 $ - Trip // [1.219 $ - Eurowings + Scooot + Qatar]
07) Dohop - 1.244 $ - ?? // [n/a]
08) GoToGate - 1.248 $ - Booking // [1.128 $ - Eurowings + Scooot + Qatar]
09) Jetradar - 1.254 $ - GoTravel // [n/a]
10) Opodo - 1.279 $ - eDreams // [n/a]
11) Google Flights - 1.286 $ - Alphabet // [1.116 $ - Eurowings + Scooot + Qatar]
12) Lastminute - 1.294 $ - Lastminute // [n/a]
13) eDreams - 1.295 $ - eDreams // [n/a]
14) seat24 - 1.297 $ ?? // [0.992 $ - Eurowings + Scooot + Qatar]
15) eSky - 1.302 $ - eSky // [n/a]
16) FlyHub - 1.563 $ - FlyHub // [n/a]
2) FIND ALMOST ALL
17) Kayak = Momondo - 1.294 - 1.262 - Booking // [1.209 $ - Eurowings + Scooot / Qatar]
18) Priceline = Cheapflights = Agoda - 1.262 - 1.296 $ - Booking // [n/a]
19) Travelocity = Hotwire = Orbitz = Cheaptickets - 1.262 $ - Expedia // [0.961 $ - Turkish + Oman Air / Oman Air + Qatar]
20) Expedia - 1.296 $ - Expedia // [n/a]
21) Cheapoair = Onetravel - 1.304 $ - TravelFare // [0.981 $ - Austrian + Eva Air]
22) Webjet - 1.367 $ - WebJet // [n/a]
3) OTHERS
23) Hopper
Conclusion
The best Direct Price
01) Student Agency = Kralovna - 0.903 $ - Student Agency // [0.928 $ - Oman Air]
02) Letenky - 0.909 $ - Student Agency // [0.792 $ - Air India from Vienna]
The best Combination Price
04) Pelikan - 1.176 $ - Pelikan // [0.805 $ - Air India from Vienna]
14) seat24 - 1.297 $ ?? // [0.992 $ - Eurowings + Scooot + Qatar]
19) Travelocity = Hotwire = Orbitz = Cheaptickets - 1.262 $ - Expedia // [0.961 $ - Turkish + Oman Air / Oman Air + Qatar]
21) Cheapoair = Onetravel - 1.304 $ - TravelFare // [0.981 $ - Austrian + Eva Air]