Short answer: If you need to arrive at Dubai International (DXB) specifically, the main low‑cost carrier operating CMB–DXB is Flydubai — but its on‑time performance for Colombo flights is mixed (roughly ~60–75% on‑time in recent FlightStats reports). If you’re flexible about arrival airport and will accept Sharjah (SHJ), Air Arabia (a true LCC) often posts better on‑time numbers on the Colombo–Sharjah sector (some CMB–SHJ flights showing ~70–87% on‑time in recent samples). (FlightStats.com)

Details and practical recommendation

• Flydubai is the principal budget carrier that flies into Dubai (DXB) from Colombo. FlightStats data for individual CMB–DXB Flydubai flights in recent reporting windows show on‑time rates commonly between the high 50s and low 70s percent (average delays in the 20–30 minute range for some flights). That means moderate reliability — acceptable but expect occasional delays. (FlightStats.com)
• Air Arabia operates multiple daily nonstop flights Colombo ↔ Sharjah (SHJ). FlightStats and other schedule trackers show many of those specific flights reporting on‑time rates commonly in the 70–80%+ range in recent samples. Because Sharjah is about 30–60 minutes by road from much of Dubai, Air Arabia is often the more reliable low‑cost option if you can land at SHJ. (FlightStats.com)
• If “most reliable” means highest probability of being on time and lowest average delay regardless of carrier class, SriLankan Airlines (full service) has shown very strong on‑time figures on the Colombo–UAE sectors in the same datasets — but it’s not a budget carrier. If price is less critical than schedule reliability, consider SriLankan. (FlightStats.com)

Quick decision guide

• Must arrive at DXB (Dubai Intl): Flydubai is the budget option; moderately reliable. Expect some variability. (FlightStats.com)
• Can arrive at SHJ (Sharjah) and transfer to Dubai: Air Arabia is often the more reliable low‑cost choice. (FlightStats.com)
• Want the best on‑time reliability regardless of budget: consider SriLankan (full‑service). (FlightStats.com)

If you want, I can:

• Check specific flight numbers or dates (OTP varies by flight and time of year), or
• Compare current fares + schedules for your travel date and show the most reliable low‑cost option for that exact date. (I’ll need the travel date if you want that.)