The Great Airport Mystery by Franklin W. Dixon

helicopter’s whirling rotor blades was heard faintly in the distance. The Hardys darted from the cave and into the center of the pasture. They waved their arms vigorously as the craft passed overhead. In response, it turned into a descending spiral and the pilot set the craft down gently a few yards away from the boys. The door opened and Mr. Allen stepped out.
    â€œYou two have discovered something of great importance?” he asked eagerly.
    â€œYes, we have,” Frank answered. “We’ve captured two members of the gang we think is involved in the platinum thefts, and what may be the stolen merchandise.”
    â€œCongratulations!” Mr. Allen said. “You don’t waste any time when working on a case.”
    â€œThanks,” Frank replied. “But the mystery is far from being solved. There’s a great deal more that we’ll have to uncover.”
    The sleuths took the executive to the cave. “Incredible!” he commented, awe-stricken. “How did you ever manage to discover this hideout?”
    â€œWe’ll fill you in on the details later,” Frank said. “Right now, we’d like you to check out the contents of the wooden boxes we found here.”
    As they came to the plane, he stared in astonishment, but did not pause. The three hurried on to the waiting group, and the executive was introduced.
    As Mr. Allen and the two boys entered the storage room, Barney and Anchor looked very uneasy. The president of Stanwide took several folded sheets of paper from his coat pocket.
    â€œThese are copies of the bills of lading of the missing shipments,” he said. “I’ve checked off what materials made up the shortages.”
    The Hardys lifted the lid of the box they had been opening, and Mr. Allen read off a list of items and quantities. The contents tallied exactly with some of the missing platinum parts! Two other boxes were opened, disclosing more of the items on the list!
    Frank spoke to the officers. “I’d say there’s enough evidence here to arrest Barney and Anchor.”
    â€œYou’re right,” said one of the State Police officers.
    Gripping each of the handcuffed men by an arm, two of the troopers began walking them out of the cave.
    Suddenly Anchor broke his silence. “Wait a minute!” he shouted. “You can’t do this! We’re not the head guys in this racket!”
    â€œWho else is in this with you?” Frank prodded. “Give us their names!”
    Barney nudged Anchor with his elbow, signaling him to keep silent. “I don’t know who they are,” Anchor mumbled meekly.
    Refusing to say any more, the two suspects were led away. Mr. Allen clapped the Hardys on their shoulders. “This has been a great job on your part, fellows.” The brothers grinned.
    With their help Mr. Allen checked several more boxes and found that they also contained stolen parts. Joe suggested that they load as many of them as they could aboard Mack’s helicopter for transport back to Stanwide. One of the troopers offered the use of the police helicopter to aid in the operation. He also told the Hardys that several men would be assigned to stand guard over the cave.
    Still amazed by the camouflaged hideout, Mr. Allen took a flashlight and scanned the surroundings. For the first time he took a close look at the airplane stored there. What he saw seemed to startle him.
    â€œIt’s hard to believe!” the executive murmured. “But it is!”
    â€œWhat is?” asked Frank, curious.
    â€œâ€˜This airplane!” Mr. Allen answered, playing the beam of light across its sleek lines. “This was Clint Hill’s!”
    â€œBut I thought that crashed!” Joe said in amazement.
    Mr. Allen beckoned the Hardys to step closer to the plane. He pointed a trembling finger at something on the side of the cowling. It appeared to be a small decal, in the shape of an eagle.
    â€œClint put