Things are not that simple.Inquirer wrote: Besides, you needn't be having the absolute lowest fares to attract passengers; what's important is that the spread isn't too big and the product differences between the 2 airlines seem to justify this spread.
This seems to be the case, regardless the period and who has the absolute upper hand at any given time.
But again, don't limit your scope to just the 2 in this discussion: have a look at all the others and their relative positioning in the line up of booking engines: airlines like vueling for instance suddenly have a problem, it seems!
I have had a look at the prices - choosing at random Lisbon as destination and the week 11-17 January.
Brussels Airlines : no 69 euros available; day return from 129,74 to 165,39 euros; longer stays inside that week : from 79,74 to 129,74 euros.
Ryanair : BRU-LIS from 30,59 to 43,85 euros; LIS-BRU from 30,59 to 52,01 euros.
Return from 61,18 to 95,86 (day return possible at 61,18 euros)
Vueling : BRU-LIS from 29,99 to 39,99 euros; LIS-BRU from 29,99 to 49,99 euros (prices for direct flights only - no direct flight on tuesday). No day return possible (only one direct flight daily).
Return from 59,98 to 79,98 euros. Add a 5 euros administrative fee plus 1,95 euro credit card fee.
Thus, more than ever, it's essential to compare prices according to one's own requirement.