Iberia saw a 17.3% rise in passenger numbers on its longhaul flights last month, with Latin American routes spearheading the growth with a jump of 22.4%.
The Spanish airline saw an overall increase in revenue passenger kilometres of 10%.
Iberia fared better than its merger partner British Airways, which saw an increase in revenue passenger kilometres (RPK) of 1.3%.
The figure represents progress for BA, however, which has for a long time seen a fall in figures - last month RPK fell 2.9%, while in July it fell 2.6%.
The merger saw important developments last month, with the appointment of the board of directors for the joint company on September 22.
Officials say the finalisation of the deal is on track for the end of this year.
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