Left upper lobe collapse (atelectasis) is seen. This is the classic pattern. Note the soft-tissue-density structure in the upper anterior left hemithorax.
On the lateral view it is clearly demarcated by a linear interface with aerated lung. A density is seen connecting it to the hilum, called the "mediastinal wedge" by Felson. (See annotated image.)
On the PA view it is seen as homogeneous increased density of the upper left hemithorax. It obscures anterior mediastinal structures, namely the anterior aortic arch, main pulmonary artery segment, and upper left heart border. Note the preservation of the outline of the posterior part of the aortic arch and the descending thoracic aorta. The left hilum is markedly displaced upward. (See annotated image.)
In this case, unlike the other example, the inferior left heart border is still clearly seen on the PA view. This is because the degree of collapse is greater, as can be seen on the lateral image; the atelectatic lobe is retracted more anteriorly, and the left heart border is in contact with aerated lung.
Evidence of the prior right upper lobectomy is seen, including elevation of the right hilum and hilar surgical clips. Absence of the right upper lobe probably explains the absence of mediastinal shift, a finding commonly, but not universally, seen in left upper lobe collapse.