We consider operators of the form: ∫ − ∞ ∞ F t φ ( t ) d t \int _{ - \infty }^\infty {{F_t}\varphi (t)\;dt} , where F t {F_t} is a 1 1 -parameter family of Fourier integral operators and φ ( t ) d t \varphi (t)\;dt a tempered distribution on the real line and show that these operators are sums of pseudo-differential and Fourier integral operators. Here, we give the typical case where φ ( t ) d t = p . v . { 1 / t } \varphi (t)\;dt = {\text {p}}.{\text {v}}.\left \{ {1/t} \right \} . An application to singular integrals on variable curves is given.