Fuel costs typically account for up to a fifth of an airline's operating expenses and, if the Opec cartel sticks to its guns, keeping planes in the air will become more costly in the long run. On the flipside, oil and gas producers nosed higher. PetroChina, an Asian favourite of legendary investor Warren Buffett, gained 10 cents or 4% to HK$2.625, oil producer CNOOC added 10 cents to HK$13.75, a 0.8% gain, and Sinopec was better by five cents at HK$2.175, a rise of 2.4%.