Airline-sector stocks gained ground Thursday amid optimism about a pension bill that stands to ease the financial pinch facing U.S. carriers and another decline in oil prices. Shares in American Airlines parent AMR Corp. and Continental Air Airlines Inc. were leading the charge. In midday New York Stock Exchange trading, AMR rose 85 cents, or 7.4 percent, to close at $12.41, while Continental advanced rose $1.38, or 13 percent, to close at $11.88. According to the latest version of a pension reform bill in the U.S. Senate, the two carriers will be given extra time to pay off underfunding in their pension plans. The same privilege was granted last week to Northwest Airlines Corp. and Delta Air Lines Inc. after the two carriers filed for bankruptcy protection.