| as monitoring from planes | 15 | other |
| in 1990 | 8 | temporal |
| during that time | 8 | temporal |
| tower → be → closed | 123 |
| tower → be closed for → safety reasons | 4 |
| negative | neutral | positive |
| 0.232 | 0.665 | 0.102 |
| Raw frequency | 127 |
| Normalized frequency | 0.596 |
| Modifier score | 1.000 |
| Perplexity | 179.098 |