Looking to fly from Osaka to Taipei on June 2nd. Have looked at Google flights and there are a number of options. Direct flights are about 3 hours. Thai Vietjet, Thai Lion, and Tigerair Taiwan are in the $100 range, one way. China Airlines is double but may not have a good time. Any suggestions. We don't need luxury on a three hour flight but would like some kind of reliability.

Click on the v arrow for each flight here:
Osaka to Taipei City | Google Flights

FWIW, for Thai Vietjet and Air Asia X it says:
Often delayed by 30+ min

Thanks mrwunrfl - Have you ever used any of these airlines?

Among the nonstops only JetStar, but that was in Australia. I think that was something of a different company from JetStar Japan. One flight was ok, second flight was delayed for several hours.

IME Vietjet are one of the worst airlines in Asia. Cancellations are frequent, customer service/comms very poor I would avoid at all costs. No experience of Thai Lion or Tigerair.

We have always had good experience using Air Asia having flown them probably 30-40 times all over Asia. They would be my choice even if a connection was required, though I am pretty sure you will find direct flights from Taipei to Osaka.

I am currently looking at a trip to Japan or Taiwan (or combining the two) this autumn. So far only at the point of looking at flights from London but would be very interested if you do find a decent routing.

Here is a multi-city GF fare search from London to Taipei and three airports in Japan.
London to Fukuoka and 3 more | Google Flights

The USD prices below are what I see at GF. The GBP prices are what I get when I click through to China Airlines.

LON-TPE, FUK-LON
USD 1088
GBP 804.69
This is an open jaw, London to Taipei returning from Fukuoka. You would need to add a one-way TPE-Japan. Note that the fare has an overnight connection in Taipei.

Simple roundtrip
LON-TPE-LON
USD 1000
GBP 739.39
You would need to add flights both ways between TPE and Japan.

Those GBP fares are the lowest (Basic) for the dates I chose. The also have Standard and Flex. I noticed that the return flight had a Discount fare option but it was a bit higher than Basic and had higher fees for changes and cancellation (and no points earning).