LCC is on NYSE. AAMRQ is "pink sheets" which is an unregulated exchange. They would have been halted if under NYSE or NASDAQ rules. Halts are designed to prevent volatility and price spikes during major news announcements. Also to c-block unethical insiders who may try to benefit from non-public news. NYSE is the exhange with humans on the floor, standing around buying and selling orders. NASDAQ is all computer based. NYSE is more "old school" and more strict with things like this.