By Pete Najarian, co-founder of OptionMonsterARLINGTON, Va. ( TheStreet) -- Traders were buying AES ( AES) calls in large numbers Thursday, the second time this week that the international power company has seen upside option activity. OptionMonster's real-time systems showed that 20,350 calls changed hands at the April 12.50 strike against open interest of just 692 contracts, clearly indicating new positions. More than 15,400 of those calls traded in a strong buying pattern, most of them going for 15 cents to 35 cents. AES closed Thursday up 3.02% to $11.60 and ticked up another 0.26% in after-hours trading. The stock dropped sharply after hitting its 52-week high at $15.44 in October and had been trading sideways until gapping down early last month. The April 12.50 calls alone represented six times the total average volume of 3,418 contracts a day for all AES options. The average daily call volume at that strike is only 51 contracts. For those calls to turn a profit, the stock would need to gain roughly 10% by the time the options expire in mid-April. AES is scheduled to release its next earnings report on May 3. A longer-term trader also was bullish on the name in January 2011 contracts, buying 4,575 of the January 10 calls for $2.50 in three minutes. On Monday, we reported call buying at the January 12.50 strike. Overall, calls in the name outnumbered puts by more than 26 to 1. At the time of publication, Najarian owned AES calls.