Dallas-based Southwest Airlines Co. and Fort Worth-based American Airlines Inc. could be impacted by a proposed increase in passenger-ticket taxes being considered by President Barack Obama.In Obama’s proposed fiscal 2012 budget, there will likely be a cut of $1.1 billion — or 31 percent — of federal grants for airport construction projects, according to media reports.Obama may also suggest the passenger facility charges included in airline ticket prices be increased from $4.50 a flight segment to as much as $7 to recoup lost revenue and bring in...